31876

Appears in sequences

• Even pseudoprimes to base 9.at n=31A090083
• Structured truncated tetrahedral numbers.at n=25A100156
• First of two complementary trees generated by the triangular numbers. The second tree is A183232.at n=33A183231
• T(n,k)=Number of nXk 0..3 arrays with no element equal to one plus the sum of elements to its left or one plus the sum of the elements above it or one plus the sum of the elements diagonally to its northwest or one plus the sum of the elements antidiagonally to its northeast, modulo 4.at n=29A240260
• Number of 2Xn 0..3 arrays with no element equal to one plus the sum of elements to its left or one plus the sum of the elements above it or one plus the sum of the elements diagonally to its northwest or one plus the sum of the elements antidiagonally to its northeast, modulo 4.at n=6A240261
• Number of (n+2)X(5+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=12A259003
• 100-gonal numbers: a(n) = 98*n*(n-1)/2 + n.at n=26A261276
• Numbers k such that 9^k - 3^k - 1 is prime.at n=21A265481
• Pseudoprimes to base 9 that are not squarefree.at n=30A306448
• Number of non-isomorphic strict connected multiset partitions of weight n.at n=11A319557