19589

Appears in sequences

• Numbers n such that 1n1, 3n3, 7n7 and 9n9 are all primes.at n=29A059677
• Numbers k that divide the sum of digits of 13^k.at n=39A175525
• Number of (n+2)X3 0..1 arrays with every 3X3 subblock having three equal elements in a row horizontally, vertically or nw-to-se diagonally exactly three ways, and new values 0..1 introduced in row major order.at n=14A204374
• Irregular array read by rows. a(n) is the largest element in the primitive Collatz-like 3x-k cycle associated with A226623(n).at n=11A226624
• Compound filter (summands of A004001 & summands of A005185): a(n) = P(A286541(n), A286559(n)), where P(n,k) is sequence A000027 used as a pairing function, with a(1) = a(2) = 0.at n=23A286560
• Number of nonnegative solutions to (x_1)^2 + (x_2)^2 + ... + (x_7)^2 <= n.at n=30A341402