40020

Appears in sequences

• Coefficient of x^4 in expansion of (1+x+x^2)^n.at n=28A005712
• Numbers k such that the least term in the periodic part of the continued fraction for sqrt(k) is 20.at n=19A031698
• Base-9 palindromes that start with 6.at n=28A043033
• a(n) = concatenation of n^2 and n.at n=19A055436
• a(n) = 100*n^2 + n.at n=19A055438
• Sum of factorials of digits of n equals the largest prime factor of n.at n=18A074257
• a(n) = 400*n^2 + 2*n.at n=9A158312
• a(n) = 400*n^2 + 20.at n=10A158601
• Molecular topological indices of the Moebius ladders.at n=22A192833
• Molecular topological indices of the prism graphs Y_n.at n=22A192838
• Sequence f_n from a paper by Robert Osburn and Brundaban Sahu.at n=7A224529
• Sequence A261220 shown in factorial base: a(n) = A007623(A261220(n)).at n=57A260743
• Number of nXnXn triangular 0..2 arrays with some element plus some adjacent element totalling 2 exactly once.at n=5A270251
• T(n,k)=Number of nXnXn triangular 0..k arrays with some element plus some adjacent element totalling k exactly once.at n=26A270256
• Number of 6X6X6 triangular 0..n arrays with some element plus some adjacent element totalling n exactly once.at n=1A270261
• Number of active (ON, black) cells at stage 2^n-1 of the two-dimensional cellular automaton defined by "Rule 417", based on the 5-celled von Neumann neighborhood.at n=7A272017
• a(n) = trinomial(2*n, 4) = (1/6)*n*(2*n - 1)*(2*n^2 + 7*n - 3).at n=15A302710