

A226489


a(n) = n*(15*n11)/2.


5



0, 2, 19, 51, 98, 160, 237, 329, 436, 558, 695, 847, 1014, 1196, 1393, 1605, 1832, 2074, 2331, 2603, 2890, 3192, 3509, 3841, 4188, 4550, 4927, 5319, 5726, 6148, 6585, 7037, 7504, 7986, 8483, 8995, 9522, 10064, 10621, 11193, 11780, 12382, 12999, 13631, 14278
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

0,2


COMMENTS

Sum of nth 9gonal (nonagonal) number and nth 10gonal (decagonal) number.
Sum of reciprocals of a(n), for n>0: 0.614629940137818703272919217222307...


LINKS

Bruno Berselli, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (3,3,1).


FORMULA

G.f.: x*(2+13*x)/(1x)^3.
a(n) + a(n) = A064761(n).


MATHEMATICA

Table[n (15 n  11)/2, {n, 0, 50}]
CoefficientList[Series[x (2 + 13 x) / (1  x)^3, {x, 0, 45}], x] (* Vincenzo Librandi, Aug 18 2013 *)


PROG

(MAGMA) [n*(15*n11)/2: n in [0..50]];
(MAGMA) I:=[0, 2, 19]; [n le 3 select I[n] else 3*Self(n1)3*Self(n2)+Self(n3): n in [1..45]]; // Vincenzo Librandi, Aug 18 2013
(PARI) a(n)=n*(15*n11)/2 \\ Charles R Greathouse IV, Oct 07 2015


CROSSREFS

Cf. A001106, A001107.
Cf. numbers of the form n*(n*kk+4))/2, this sequence is the case k=15: see list in A226488.
Sequence in context: A307554 A031911 A136685 * A125201 A215392 A140544
Adjacent sequences: A226486 A226487 A226488 * A226490 A226491 A226492


KEYWORD

nonn,easy


AUTHOR

Bruno Berselli, Jun 09 2013


STATUS

approved



