Sequences

Sum of digits of the n-th tetrahedral number.

Tetrahedral numbers written backwards.

Sum of digits of pentagonal numbers.

Pentagonal numbers written backwards.

Sum of digits of n^3.

Cubes written backwards.

Sum of digits of 3^n.

Powers of 3 written backwards.

a(n+1) = a(n)*(a(n)+1).

Values of m for which a regular polygon with m sides cannot be constructed with ruler and compass.

Reversals of Fibonacci numbers (sorted).

a(n) = 2^(2n+1).

Triangle of coefficients of Euler polynomials E_2n(x) (exponents in increasing order).

Triangle of coefficients of Euler polynomials E_2n(x) (exponents in decreasing order).

Triangle of coefficients of Euler polynomials 2^n*E_n(x) (exponents in increasing order).

Triangle of coefficients of Euler polynomials 2^n*E_n(x) (exponents in decreasing order).

Omit 1's from n.

Omit 2's from n.

Omit 3's from n.

Omit 4's from n.

Omit 5's from n.

Omit 6's from n.

Omit 7's from n.

Omit 8's from n.

Omit 9's from n.

Arrange digits of n in increasing order, then (for n > 0) omit the zeros.

Arrange digits of n in decreasing order.

a(n) = 7*a(n-1) - a(n-2) with a(0) = 0, a(1) = 1.

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

a(n) = 10*a(n-1) - a(n-2); a(0) = 0, a(1) = 1.

Expansion of 1/(1 - 11*x + x^2).

Expansion of 1/(1 - 12*x + x^2).

Numbers obtained by reversing digits of factorial numbers.

a(n) = -(-1)^n*2*(2*n+1)!*Bernoulli(2*n)/(n!*2^n).

Number of partitions of 1/n into 3 reciprocals of positive integers.

The numbers not expressible as the sum of 4 distinct nonzero squares can be written D*4^n union E. This is D.

The numbers not expressible as the sum of 4 distinct nonzero squares can be written D*4^n union E. This is E.

Triangle read by rows. T(n, k) = n - k if n - k < k, otherwise k.

Table of x AND y, where (x,y) = (0,0),(0,1),(1,0),(0,2),(1,1),(2,0),...

Table of [ x/y ], where (x,y) = (1,1),(1,2),(2,1),(1,3),(2,2),(3,1),...

Continued fraction for Sum_{k>=0} 1/3^(2^k).

Accept one, reject one, accept two, reject two, ...

Skip 1, take 1, skip 2, take 2, skip 3, take 3, etc.

Numbers n such that 54*10^n + 1 is prime.

Number of permutations of length n with spread 0.

Number of permutations of length n with spread 1.

Number of permutations of length n with spread 2.

a(0) = 1, a(n) = sum of digits of all previous terms.

a(n) = n * (2*n - 1)!! - Sum_{k=0..n-1} a(k) * (2*n - 2*k - 1)!!.

For m=2,3,..., write m in bases m,m-1,...,3,2.