131905

Appears in sequences

• Heptagonal numbers A000566 which are the sum of two other heptagonal numbers > 0.at n=33A133251
• Expansion of x^4*(1-2*x+x^4)/((1+x)*(1-2*x)^2*(1-x-x^2)).at n=19A219753
• For bases b = 2, 3, ..., n, let the base-b expansion of n be [c_{1,b} c_{2,b} .. c_{r_b,b}], with the most significant "digit" on the left, 0 <= c_{i,b} < b, and c_{1,b} != 0; then a(n) is the number whose base-n expansion is the sum of all those expansions, regarding the c_{i,j} as integers mod n.at n=17A247880
• Heptagonal numbers which are products of four distinct primes.at n=16A351867