21657

Appears in sequences

• a(n) = Catalan(n) + Catalan(n+1) - 1.at n=9A000778
• Numbers k such that the continued fraction for sqrt(k) has even period and if the last term of the periodic part is deleted the central term is 98.at n=31A031596
• Numbers k such that 131*2^k+1 is prime.at n=28A032415
• Largest eigenvalue, rounded to the nearest integer, of a rank n matrix of 1..n^2 filled successively along rows.at n=34A072333
• a(0)=1, a(n+1)=ceiling((1+1/n)^n*a(n)).at n=11A092247
• Numbers k such that tau(k) = tau(k+1) mod 691, where tau is Ramanujan's tau function A000594.at n=33A121733
• Numbers m such that m*reversal(m) contains every decimal digit exactly once.at n=6A178929
• Partial sums of A299279.at n=20A299280