26884

Appears in sequences

• Number of bipartite partitions.at n=18A002763
• 9-gonal heptagonal numbers (A000566).at n=1A048921
• a(n) = Sum_{k=1..n} lcm(n,k).at n=43A051193
• Smallest number m such that m^2+1 is divisible by A002144(n)^2 (= squares of primes congruent to 1 mod 4).at n=22A059321
• Heptagonal numbers with only even digits.at n=5A117994
• a(n) = p(n+1)^2 + 2*p(n) + 1; p(n) is the n-th prime number and n >= 1.at n=36A155819
• a(n) = Sum_{k=0..n-1} {[x^k] A(x)^(n-k)} * {[x^(n-k-1)] A(x)^(k+1)} for n>0, with a(0)=1, where g.f. A(x) = Sum_{n>=0} a(n)*x^n.at n=7A161881
• a(n) = the smallest k such that k^2+1 = p*A002144(n)^2, p prime of A002144 .at n=22A174492
• Triangle T(n,k) read by rows of the smallest n-gonal number greater than 1 that is also k-gonal, or 0 if none exists, for 3 <= k <= n.at n=25A189216
• Numbers n such that n^2 + 1 has two distinct prime divisors less than n.at n=26A263876