21550

Appears in sequences

• Numbers k such that 15*2^k + 1 is prime.at n=32A002258
• Expansion of Product_{m>=1} (1+m*q^m)^-20.at n=6A022712
• Coefficient of x^2 in the polynomial (x-p(n))*(x-p(n+1))*(x-p(n+2))*(x-p(n+3)), where p(k) is the k-th prime.at n=15A127348
• Expansion of g.f. 1/((1-x^2+x^3+x^4-x^5)*(1-x-x^2+x^3-x^5)).at n=28A147598
• Indices of primes followed by a gap (distance to next larger prime) of 44.at n=21A320720
• Position of n-th appearance of 2n in the sequence of prime gaps (A001223). If 2n does not appear at least n times, set a(n) = -1.at n=21A356223