19810

Appears in sequences

• Weird numbers: abundant (A005101) but not pseudoperfect (A005835).at n=35A006037
• Maximal length of rook tour on an n X n board.at n=30A006071
• Column 4 of A061315.at n=7A061319
• Unitary weird numbers: unitary abundant (A034683) but not unitary pseudoperfect (A293188).at n=32A064114
• Sum of terms in periodic part of continued fraction expansion of square root of 1+2^n.at n=24A077628
• Triangle read by rows: row n gives coefficients of expansion of q-tangent number T_{2n+1}(q) in powers of q.at n=43A143194
• Triangle read by rows: row n gives coefficients of expansion of q-tangent number T_{2n+1}(q) in powers of q.at n=52A143194
• The Wiener index of a chain of n triangles (i.e., joined like VVV..VV; here V is a triangle!).at n=29A143941
• Expansion of g.f. 1 - 2*x*(-7 - 10*x + x^2)/(x - 1)^4.at n=15A152100
• Number of length 4+2 0..n arrays with some pair in every consecutive three terms totalling exactly n.at n=8A245873
• Positions of 2's in A264977; positions of 3's in A277330.at n=56A277712
• Bi-unitary weird numbers: bi-unitary abundant numbers (A292982) that are not bi-unitary pseudoperfect (A292985).at n=37A292986
• Numbers k such that Bernoulli number B_{k} has denominator 4686.at n=14A295770
• a(1) = 27846; thereafter a(n+1) = a(n) # n, where # is an operation that cycles through division, addition, subtraction and multiplication.at n=10A327962
• Nonexponential weird numbers: nonexponential abundant numbers (A348604) that are not equal to the sum of any subset of their nonexponential divisors.at n=29A348631
• (1+e)-weird numbers: (1+e)-abundant numbers k such that no subset of the aliquot (1+e)-divisors of k sums to k.at n=30A349285