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A123028 a(n) = (3*n^2 + 3*n + 1)*a(n-2), for n>2, with a(0) = a(1) = 1. 1
1, 1, 19, 37, 1159, 3367, 147193, 569023, 31940881, 154205233, 10572431611, 61219477501, 4958470425559, 33487054193047, 3128794838527729, 24144166073186887, 2556225383077154593, 22188488621258749153 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

LINKS

G. C. Greubel, Table of n, a(n) for n = 0..400

FORMULA

a(n) = n!*b(n), where b(n) = (3*n*(n+1) + 1)*b(n-2)/(n*(n-1)), b(0) = b(1) = 1.

a(n) = A003215(n) * a(n-2), n>2.

MATHEMATICA

a[n_]:= a[n]= If[n<2, 1, (3*n^2 +3*n +1)*a[n-2]]; Table[a[n], {n, 0, 30}]

PROG

(Magma)

function a(n)

  if n lt 2 then return 1;

  else return (3*n*(n+1) +1)*a(n-2);

  end if; return a;

end function;

[a(n): n in [0..30]]; # G. C. Greubel, Jul 20 2021

(Sage)

def a(n): return 1 if (n<2) else (3*n*(n+1) +1)*a(n-2)

[a(n) for n in (0..30)] # G. C. Greubel, Jul 20 2021

CROSSREFS

Cf. A003215, A123025.

Sequence in context: A111441 A144594 A287310 * A067205 A196185 A040342

Adjacent sequences:  A123025 A123026 A123027 * A123029 A123030 A123031

KEYWORD

nonn,easy

AUTHOR

Roger L. Bagula, Sep 25 2006

EXTENSIONS

Definition replaced by recurrence - the Assoc. Eds. of the OEIS, Mar 27 2010

Edited by G. C. Greubel, Jul 20 2021

STATUS

approved

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Last modified October 3 22:17 EDT 2022. Contains 357237 sequences. (Running on oeis4.)