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A272399 The intersection of hexagonal numbers (A000384) and centered 9-gonal numbers (A060544). 2
1, 28, 91, 190, 325, 496, 703, 946, 1225, 1540, 1891, 2278, 2701, 3160, 3655, 4186, 4753, 5356, 5995, 6670, 7381, 8128, 8911, 9730, 10585, 11476, 12403, 13366, 14365, 15400, 16471, 17578, 18721, 19900, 21115, 22366, 23653, 24976, 26335, 27730, 29161, 30628 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Colin Barker, Table of n, a(n) for n = 1..1000

Index entries for linear recurrences with constant coefficients, signature (3,-3,1).

FORMULA

a(n) = A272398(4*n-3).

a(n) = 10-27*n+18*n^2.

a(n) = 3*a(n-1)-3*a(n-2)+a(n-3) for n>3.

G.f.: x*(1+25*x+10*x^2) / (1-x)^3.

a(n) = A000384(3*n-2) = A060544(2*n-1). - Robert Israel, Apr 28 2016

E.g.f.: (9*x*(2*x - 1) + 10)*exp(x) - 10. - Ilya Gutkovskiy, Apr 28 2016

MATHEMATICA

Rest@ CoefficientList[Series[x (1 + 25 x + 10 x^2)/(1 - x)^3, {x, 0, 42}], x] (* Michael De Vlieger, Apr 28 2016 *)

PROG

(PARI) lista(nn) = for(n=1, nn, print1(10-27*n+18*n^2, ", ")); \\ Altug Alkan, Apr 28 2016

(PARI) a(n)=18*n^2-27*n+10 \\ Charles R Greathouse IV, Apr 28 2016

(PARI) Vec(x*(1+25*x+10*x^2) / (1-x)^3 + O(x^50)) \\ Colin Barker, Apr 29 2016

CROSSREFS

Cf. A000384, A060544, A272398 (union).

Sequence in context: A164689 A096384 A065655 * A113958 A219815 A044215

Adjacent sequences:  A272396 A272397 A272398 * A272400 A272401 A272402

KEYWORD

nonn,easy

AUTHOR

Colin Barker, Apr 28 2016

STATUS

approved

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Last modified October 16 03:26 EDT 2019. Contains 328038 sequences. (Running on oeis4.)