Sequences

Single (or isolated or non-twin) primes: Primes p such that neither p-2 nor p+2 is prime.

a(n) is the smallest number greater than a(n-1) that is expressible as the sum of two squares in more ways than a(n-1).

Primes of the form floor(e*10^k), i.e., formed by concatenation of an initial segment of the decimal expansion of e.

a(n) = initial prime of n consecutive primes such that first and last have same digit sum.

Pi = Sum_{n >= 0} a(n)/n!.

Continued fraction for Wirsing's constant.

(2^2^...^2) (n times) + 1.

a(n) = phi(n) * (sigma(n) - n).

a(n) = floor(n*(n+2)*(2*n-1)/8).

Primes of form 8n+1, that is, primes congruent to 1 mod 8.

Primes == 3 (mod 8).

Primes of the form 8k + 5.

Primes of the form 8n+7, that is, primes congruent to -1 mod 8.

Primes in A092845 (decimal expansion of Pi written backwards).

Decimal expansion of log_10(2).

Decimal expansion of log_2 e.

a(n) = n*(a(n-1) + 1), a(0) = 0.

Numbers that are not the sum of 4 hexagonal numbers.

Primes of the form 6k-1.

Prime triples: p; p+2 or p+4; p+6 all prime.

Prime quadruples: numbers k such that k, k+2, k+6, k+8 are all prime.

a(n) = n*(n-1)*(n-2) (or n!/(n-3)!).

Handsome numbers: sum of positive powers of its digits; a(n) = Sum_{i=1..k} d[i]^e[i] where d[1..k] are the decimal digits of a(n), e[i] > 0.

a(n) = (5*n + 1)^2 + 4*n + 1.

Positive even numbers that are not the sum of a pair of twin primes.

Smallest pseudoprime ( > n ) to base n: smallest composite number m > n such that n^(m-1)-1 is divisible by m.

Numbers that are not the sum of 3 hexagonal numbers (probably finite).

Number of proper covers of an n-set.

A self-generating sequence: there are a(n) 3's between successive 2's.

a(n) = first n-fold perfect (or n-multiperfect) number.

Wilson primes: primes p such that (p-1)! == -1 (mod p^2).

Incrementally largest terms in the continued fraction for Pi-2 (cf. A001203).

Successive integers produced by Conway's PRIMEGAME.

Frequency of n-th largest distance in N times N grid, N > n.

Frequency of n-th largest distance in N times N times N grid, N > n.

Number of chess games with n plies (another version).

Number of steps to compute n-th prime in PRIMEGAME (fast version).

Number of steps to compute n-th prime in PRIMEGAME (slow version).

Shifts 3 places left under exponentiation.

Number of increasing rooted connected graphs where every block is a complete graph.

Natural numbers exponentiated twice.

Shifts left when Moebius transformation applied twice.

Exponentiation of Fibonacci numbers.

Logarithmic transform of Fibonacci numbers.

Unique attractor for (RIGHT then MOBIUS) transform.

Number of standard paths of length n in composition poset.

Number of 8-ary trees with n vertices.

Shifts left when inverse Moebius transform applied twice.

Shifts 2 places left when e.g.f. is squared.

Triple factorial numbers (3*n-2)!!! with leading 1 added.