cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

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A228341 Third diagonal (T(n,2)) of triangle in A228340.

Original entry on oeis.org

1, 2, 9, 47, 291, 2084, 16963, 154751, 1564473, 17363954, 209931921, 2746478927, 38660636899, 582656032412, 9361157155491, 159722327675759, 2884363055319153, 54962620378739666, 1102136770630112473, 23199834803611101599
Offset: 2

Views

Author

N. J. A. Sloane, Aug 29 2013

Keywords

Crossrefs

Programs

  • Mathematica
    Table[FullSimplify[-2*BesselI[1+n,-2] * (BesselK[2,2] + BesselK[3,2]) + 2*(BesselI[2,2] - BesselI[3,2]) * BesselK[1+n,2]],{n,2,20}] (* Vaclav Kotesovec, Feb 14 2014 *)
  • PARI
    v = [1, 2]; for(n=4, 21, v = concat(v, n*v[n-2] + v[n-3])); v \\ Rick L. Shepherd, Jan 22 2014

Formula

a(2) = 1, a(3) = 2; thereafter, a(n) = n*a(n-1) + a(n-2).
a(n) ~ c * n!, where c = BesselI(2,2)-BesselI(3,2) = 0.47620848845888... - Vaclav Kotesovec, Feb 14 2014

Extensions

More terms from Rick L. Shepherd, Jan 22 2014
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