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A193448
a(n) = 4*(5*n^2 - 5*n + 1).
1
4, 44, 124, 244, 404, 604, 844, 1124, 1444, 1804, 2204, 2644, 3124, 3644, 4204, 4804, 5444, 6124, 6844, 7604, 8404, 9244, 10124, 11044, 12004, 13004, 14044, 15124, 16244, 17404, 18604, 19844, 21124, 22444, 23804, 25204, 26644, 28124, 29644, 31204, 32804
OFFSET
1,1
COMMENTS
The natural numbers of the form 5*n^2-1, with n odd. See also A158491 for the cases where n is even. - Giovanni Teofilatto, Oct 10 2011
FORMULA
a(n) = 4*A062786(n).
G.f.: -4*x*(1+8*x+x^2) / (x-1)^3. - R. J. Mathar, Aug 26 2011
a(n) = 3*a(n-1)-3*a(n-2)+a(n-3) for n>3. - Wesley Ivan Hurt, Nov 21 2015
MAPLE
A193448:=n->4*(5*n^2 - 5*n + 1): seq(A193448(n), n=1..50); # Wesley Ivan Hurt, Nov 21 2015
MATHEMATICA
Table[4*(5*n^2 - 5*n + 1), {n, 50}] (* Wesley Ivan Hurt, Nov 21 2015 *)
PROG
(Magma) [4*(5*n^2-5*n+1): n in [1..50]]; // Vincenzo Librandi, Aug 30 2011
(PARI) a(n) = 4*(5*n^2 - 5*n + 1) \\ Anders Hellström, Nov 21 2015
CROSSREFS
Sequence in context: A063837 A344871 A071125 * A200456 A292454 A292734
KEYWORD
nonn,easy
AUTHOR
Giovanni Teofilatto, Jul 26 2011
STATUS
approved