21073

Appears in sequences

• Number of unlabeled connected series-parallel posets with n nodes.at n=9A007453
• Strong pseudoprimes to base 89.at n=17A020315
• Number of base 21 circular n-digit numbers with adjacent digits differing by 1 or less.at n=8A124714
• a(1) = 1; thereafter a(n) is always the smallest integer > a(n-1) not leading to a contradiction, such that any five consecutive digits in the sequence sum up to a prime.at n=37A152605
• a(n) = Sum_{k=0..floor(n/5)} binomial(n,5*k)*binomial(6*k,k)/(5*k+1).at n=15A226910
• G.f.: (1 + x^4 + x^5 + x^6 + x^10 + x^11 + x^12 + x^16)/Product_{i=1..8} (1 - x^i).at n=37A256975
• Number of (n+2)X(2+2) 0..1 arrays with every 3X3 subblock sum of the two medians of the central row and column plus the two sums of the diagonal and antidiagonal nondecreasing horizontally, vertically and ne-to-sw antidiagonally.at n=2A259000
• T(n,k)=Number of (n+2)X(k+2) 0..1 arrays with every 3X3 subblock sum of the two medians of the central row and column plus the two sums of the diagonal and antidiagonal nondecreasing horizontally, vertically and ne-to-sw antidiagonally.at n=8A259006
• Number of (3+2)X(n+2) 0..1 arrays with every 3X3 subblock sum of the two medians of the central row and column plus the two sums of the diagonal and antidiagonal nondecreasing horizontally, vertically and ne-to-sw antidiagonally.at n=1A259008
• Numbers missing from A001033 despite satisfying the necessary congruence conditions (see comments).at n=35A274470