This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A116926 #9 Sep 12 2024 07:50:35 %S A116926 6,14,15,51,62,91,95,159,254,287,473,679,703,1139,1199,1339,1717,1891, %T A116926 2051,2147,2495,2651,2701,2869,3151,4313,4381,4607,5017,5267,6245, %U A116926 6683,8441,9809,10063,10637,11051,11183,12403,13119,13169,13207,13423,13427 %N A116926 Semiprimes k=p*q such that the polynomial (1+x)^k (mod k) has p+q nonzero terms. %C A116926 The maximum number of nonzero terms is p+q; all powers of x of the form k*p and l*q for k=0..q-1 and l=1..p. The even terms of this sequence are twice the Mersenne primes: 2*3, 2*7, 2*31, 2*127, 2*8191,... Similarly, for terms divisible by 3, the other prime factor has the form 2*3^k-1. Note that A007012 gives the number of nonzero terms in the polynomial (1+x)^n (mod n). %e A116926 15 is here because (1+x)^15 (mod 15) = 1+5x^3+3x^5+10x^6+10x^9+3x^10+5x^12+x^15 has 3+5 nonzero terms. %Y A116926 Cf. A007012. %K A116926 nonn %O A116926 1,1 %A A116926 _T. D. Noe_, Feb 26 2006