23270

Appears in sequences

• Sum of 11 positive 9th powers.at n=19A004800
• Numbers k such that 10^k + 4*R_k + 5 is prime, where R_k = 11...1 is the repunit (A002275) of length k.at n=18A102935
• Number of base-2 strong pseudoprimes (A001262) less than 2^n.at n=39A108797
• Expansion of Product_{k>=1} ((1 + x^(2*k-1)) / (1 - x^(2*k-1)))^k.at n=22A292037
• Triangle read by rows: Take a pentagram with all diagonals drawn, as in A331906. Then T(n,k) = number of k-sided polygons in that figure for k = 3, 4, ..., n+2.at n=27A331907