Sequences

a(n) = (binomial(4*n, 2*n) + (-1)^n*binomial(2*n, n)^2)/2.

Indices of the left-to-right maxima in A057635.

Sparsely totient numbers; numbers n such that m > n implies phi(m) > phi(n).

a(n) = binomial(2*n,n)*binomial(3*n,2*n)^4.

a(n) = Sum_{k=0..n} C(2*n-2*k,n-k)^2 * C(2*n,k)^2.

a(n) = Sum_{k=0..n} binomial(2*n-2*k,n-k)^2 * binomial(n,k)^2.

G.f.: (4/Pi^2)*EllipticK(4*x^(1/2))^2.

a(n) = floor(e*(n-1)*(n-1)!).

A036918/2.

Composite numbers n such that digit sum of n equals digit sum of sum of its prime factors (counted with multiplicity).

Numbers n such that digit sum of n equals digit sum of 'juxtaposition' and 'sum' of its prime factors (counted with multiplicity).

Even composite numbers whose digit sum equals the digit sum of (sum of prime factors, counted with multiplicity).

Odd composite numbers n such that the digit sum of n equals digit sum of sum of its prime factors (counted with multiplicity).

Digit sum of composite even number equals digit sum of juxtaposition of its prime factors (counted with multiplicity).

Digit sum of composite odd number equals digit sum of juxtaposition of its prime factors (counted with multiplicity).

Digit sum of 'even' number equals digit sum of 'sum' and 'juxtaposition' of its prime factors (counted with multiplicity).

Digit sum of 'odd' number equals digit sum of 'sum' and 'juxtaposition' of its prime factors (counted with multiplicity).

Composite numbers whose prime factors contain no digits other than 0 and 1.

Smallest n-digit prime containing only digits 0 and 1, or 0 if no such prime exists.

Smallest n-digit prime containing only digits 1 and 3, or 0 if no such prime exists.

Smallest n-digit prime containing only digits 1 and 4, or 0 if no such prime exists.

Smallest n-digit prime containing only digits 1 and 5, or 0 if no such prime exists.

Smallest n-digit prime containing only digits 1 and 6, or 0 if no such prime exists.

Smallest n-digit prime containing only digits 1 and 7, or 0 if no such prime exists.

Smallest n-digit prime containing only digits 1 and 8, or 0 if no such prime exists.

Smallest n-digit prime containing only digits 1 and 9, or 0 if no such prime exists.

Smallest n-digit prime containing only digits 2 and 3.

Smallest n-digit prime containing only digits 2 and 7, or 0 if no such prime exists.

Smallest n-digit prime containing only digits 2 and 9, or 0 if no such prime exists.

Smallest n-digit prime containing only digits 3 and 4, or 0 if no such prime exists.

Smallest n-digit prime containing only digits 3 and 5, or 0 if no such prime exists.

Smallest n-digit prime containing only digits 3 and 7, or 0 if no such prime exists.

Smallest n-digit prime containing only the digits 3 and 8, or 0 if no such prime exists.

Smallest n-digit prime containing only the digits 4 and 7, or 0 if no such prime exists.

Smallest n-digit prime containing only the digits 4 and 9, or 0 if no such prime exists.

Smallest n-digit prime containing only the digits 5 and 7, or 0 if no such prime exists.

Smallest n-digit prime containing only the digits 5 and 9, or 0 if no such prime exists.

Smallest n-digit prime containing only the digits 6 and 7, or 0 if no such prime exists.

Smallest n-digit prime containing only the digits 7 and 8, or 0 if no such prime exists.

Smallest n-digit prime containing only the digits 7 and 9, or 0 if no such prime exists.

Smallest n-digit prime containing only the digits 8 and 9, or 0 if no such prime exists.

Numbers whose binary expansion is a decimal prime.

Primes having only {0, 1, 2} as digits.

Primes with digits in {0,1,2} taken as base 3 and converted to base 10.

Numbers whose base-4 representation is the decimal representation of a prime.

Primes containing only digits from the set (0,1,2,3,4).

Primes with digits (0,...,4) taken as base 5 and converted to base 10.

Primes containing only digits from the set (0,1,2,3,4,5).

Primes with digits (0,...,5) taken as base 6 and converted to base 10.

Primes containing only digits from the set (0,1,2,3,4,5,6).