Sequences

Erroneous version of A028491.

Numbers k such that (5^k - 1)/4 is prime.

Numbers k such that (6^k - 1)/5 is prime.

Numbers k such that (7^k - 1)/6 is prime.

Numbers k such that (12^k - 1)/11 is prime.

Define predecessors of n, P(n), to consist of numbers whose binary representation is obtained from that of n by replacing 10 with 01 or changing a final 1 to a 0; then a(0)=1, a(n) = Sum a(P(n)), n>0.

Number of simple regular trivalent bicolored graphs with 2n nodes.

The coding-theoretic function A(n,6,7).

Number of atoms in a decahedron with n shells.

Numbers of points in nontrivial partial geometries.

Table of Whitney numbers W(n,k) read by antidiagonals, where W(n,k) is maximal number of pieces into which n-space is sliced by k hyperplanes, n >= 0, k >= 0.

Start with a(0)=1; replace each i with 12...i, then add 1 to final digit.

Read the terms of A004071 backwards.

Start with a(1)=1; to get a(n) replace each i in a(n-1) with 12...i, then append n.

a(n) = 2*A004001(n) - n, where A004001 is the Hofstadter-Conway $10000 sequence.

Number of Skolem sequences of order n.

Number of hooked Skolem sequences of order n.

Number of extended Skolem sequences of order n.

Number of Tuscan squares of order n.

a(n) = maximal m such that an m X n Florentine rectangle exists.

Least k such that H(k) >= n, where H(k) is the harmonic number Sum_{i=1..k} 1/i.

a(n) = n-th positive integer such that only one integer lies between exp(s(m)) and exp(s(m+1)), where s(m) = 1 + 1/2 + 1/3 + . . . + 1/m.

Numbers k such that sin(k-1) <= 0 and sin(k) > 0.

Numbers k such that cos(k-1) <= 0 and cos(k) > 0.

a(n) = n-th positive integer k such that tan(k-1) <= 0 and tan(k) > 0.

Sum of digits of Euler totient function of n.

Read n backwards (referred to as R(n) in many sequences).

Primes written backwards.

Sum of digits of number of partitions of n.

Reverse digits of number of partitions of n.

Sum of digits of Fibonacci numbers.

Fibonacci numbers written backwards.

Sum of digits of even numbers.

Even numbers written backwards.

Powers of 2 written backwards.

Sum of digits of Catalan numbers.

Catalan numbers written backwards.

Sum of digits of Bell numbers.

Bell numbers written backwards.

Sum of digits of Euler numbers.

Number of labeled nonseparable bipartite graphs on n nodes.

Number of partitions of n of the form a_1*b_1^2 + a_2*b_2^2 + ...; number of semisimple rings with p^n elements for any prime p.

Number of signed graphs with n nodes. Also number of 2-multigraphs on n nodes.

Number of nets on n unlabeled nodes.

Number of self-dual signed graphs with n nodes. Also number of self-complementary 2-multigraphs on n nodes.

Number of point-self-dual nets with 2n nodes. Also number of directed 2-multigraphs with loops on n nodes.

Number of line-self-dual nets (or edge-self-dual nets) with n nodes.

Number of self-dual nets with 2n nodes.

Number of n-node unlabeled connected graphs without endpoints.

Number of connected trivalent (or cubic) labeled graphs with 2n nodes.