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A144913 Integers which are the product of even powers of primes up to 13. 1
4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144, 169, 196, 225, 256, 324, 400, 441, 484, 576, 625, 676, 729, 784, 900, 1024, 1089, 1225, 1296, 1521, 1600, 1764, 1936, 2025, 2304, 2401, 2500, 2704, 2916, 3025, 3136, 3600, 3969, 4096, 4225, 4356, 4900, 5184, 5625 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 1..10000
FORMULA
a(n) = A080197(n+1)^2. - Rémy Sigrist, Sep 26 2020
Sum_{n>=1} 1/a(n) = -1 + Product_{primes p <= 13} p^2/(p^2-1) = 273347/442368. - Amiram Eldar, Oct 14 2020
MATHEMATICA
Select[ Range[75]^2, (fi = FactorInteger[#]; Max[ fi[[All, 1]] ] <= 13 && And @@ EvenQ /@ fi[[All, 2]]) &] (* Jean-François Alcover, Oct 10 2012 *)
eppQ[n_]:=Module[{fi=FactorInteger[n]}, Max[fi[[All, 1]]]<=13&&AllTrue[ fi[[All, 2]], EvenQ]]; Select[Range[6000], eppQ] (* Harvey P. Dale, Dec 26 2021 *)
PROG
(PARI) is(n)=if(issquare(n, &n), my(f=factor(n)[, 1]); #f && f[#f]<14, 0) \\ Charles R Greathouse IV, Jun 17 2013
CROSSREFS
Subsequence of A000290 and A080197.
Cf. A001694.
Sequence in context: A253909 A305559 A221222 * A018885 A025741 A179459
KEYWORD
easy,nice,nonn
AUTHOR
Reikku Kulon, Sep 25 2008, Sep 26 2008
STATUS
approved

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Last modified February 26 01:31 EST 2024. Contains 370335 sequences. (Running on oeis4.)