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A227863 Numbers congruent to {1,49} mod 120. 1
1, 49, 121, 169, 241, 289, 361, 409, 481, 529, 601, 649, 721, 769, 841, 889, 961, 1009, 1081, 1129, 1201, 1249, 1321, 1369, 1441, 1489, 1561, 1609, 1681, 1729, 1801, 1849, 1921, 1969, 2041, 2089, 2161, 2209, 2281, 2329, 2401, 2449, 2521, 2569, 2641, 2689 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
The squares of natural numbers not divisible by 2, 3 or 5 and therefore the squares of prime numbers >5 are confined to this sequence.
LINKS
FORMULA
G.f.: x*(1 + 48*x + 71*x^2)/((1 + x)*(1 - x)^2). [Bruno Berselli, Nov 04 2013]
a(n) = 60*n - 6*(-1)^n - 65. [Bruno Berselli, Nov 04 2013]
E.g.f.: 71 + (60*x - 65)*exp(x) - 6*exp(-x). - David Lovler, Sep 10 2022
MATHEMATICA
Table[60 n - 6 (-1)^n - 65, {n, 50}] (* Bruno Berselli, Nov 04 2013 *)
PROG
(PARI) a(n)=n\2*120+[-71, 1][n%2+1] \\ Charles R Greathouse IV, Aug 26 2014
CROSSREFS
Sequence in context: A163245 A084733 A338499 * A339131 A374290 A115557
KEYWORD
nonn,easy
AUTHOR
Gary Croft, Nov 01 2013
STATUS
approved

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Last modified July 15 16:08 EDT 2024. Contains 374333 sequences. (Running on oeis4.)