21168

Appears in sequences

• a(n) is the concatenation of n and 8n.at n=20A009470
• sec(arcsinh(x)*log(x+1))=1+12/4!*x^4-60/5!*x^5+210/6!*x^6-1260/7!*x^7...at n=8A012582
• Discriminants of totally complex sextic fields (negated).at n=13A023687
• For all n, if d is recursively applied to a(n) exactly 6 times then the fixed point of d-iteration is just reached.at n=37A036458
• Gaps of 9 in sequence A038593 (lower terms).at n=18A038657
• a(n) = n^3 - n^2.at n=28A045991
• Number of trivalent 2-connected planar graphs with 2n nodes.at n=9A058378
• Numbers that are the products of distinct substrings (>1) of themselves and do not end in 0.at n=25A059470
• Engel expansion of sinh(1/3).at n=24A068380
• Numbers k such that A069088(k) divides k.at n=40A069145
• a(n) = t(n)*t(n+1)*t(n+2), where t() are the triangular numbers.at n=6A071910
• Stirling2 triangle with scaled diagonals (powers of 2).at n=41A075497
• Sixth column of triangle A075497.at n=3A075511
• Sum of terms in n-th rows of triangle in A077159.at n=33A077162
• Smallest multiple of n^2 beginning with n.at n=20A078210
• Row sums of A081964.at n=33A081966
• Non-perfect powers k for which q = A051903(k)/A051904(k) is an integer, A051904(k) > 1.at n=3A093770
• Diagonal sums of triangle A099573.at n=29A099574
• Denominators of e.g.f.: tan(arccosh(x)) = cot(arcsinh(x)).at n=23A102062
• Denominators of e.g.f. cosec(arctanh(x)).at n=23A102077