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 A117793 Pentagonal numbers divisible by 5. 2
 0, 5, 35, 70, 145, 210, 330, 425, 590, 715, 925, 1080, 1335, 1520, 1820, 2035, 2380, 2625, 3015, 3290, 3725, 4030, 4510, 4845, 5370, 5735, 6305, 6700, 7315, 7740, 8400, 8855, 9560, 10045, 10795, 11310, 12105, 12650, 13490, 14065, 14950, 15555, 16485 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Intersection of A008587 and A000326. Their indices are given by A047215. - Michel Marcus, Feb 27 2014 LINKS Robert Israel, Table of n, a(n) for n = 1..10000 FORMULA Empirical G.f.: x^2*(5+30*x+25*x^2+15*x^3)/(1-x)^3/(1+x)^2. - Colin Barker, Feb 14 2012 a(2*n+1) = 5*n*(15*n-1)/2, a(2*n+2) = 5*(5*n+2)*(3*n+1)/2. - Robert Israel, Jun 01 2014 MATHEMATICA Select[Table[PolygonalNumber[5, n], {n, 0, 100}], Divisible[#, 5] &] (* Amiram Eldar, Mar 22 2021 *) PROG (PARI) isok(n) = ispolygonal(n, 5) && !(n % 5); \\ Michel Marcus, Feb 27 2014 CROSSREFS Cf. A000326, A008587, A047215. Sequence in context: A014632 A117985 A115707 * A145920 A153785 A090294 Adjacent sequences:  A117790 A117791 A117792 * A117794 A117795 A117796 KEYWORD easy,nonn AUTHOR Luc Stevens (lms022(AT)yahoo.com), Apr 29 2006 STATUS approved

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Last modified June 17 13:59 EDT 2021. Contains 345083 sequences. (Running on oeis4.)