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A133328 Values of n such that the sum of the 7-gonal number (5*n^2 - 3*n)/2 and the following 7-gonal number is a 7-gonal number. 3
0, 170, 13622, 6672192, 534017484, 261563278454, 20934553401986, 10253803635289356, 820676361930645528, 401969609849050063298, 32172154719470612594510, 15758012635048656946126680, 1261212808492010592999343332, 617745610917207839753008053902 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Both bisections of the sequence satisfy the recurrence relation a(n+2) = 39202*a(n+1) - a(n) + 7840.

Also nonnegative integers x in the solution to 10*x^2-5*y^2+4*x+3*y+2 = 0, the corresponding values of y being A133327. - Colin Barker, Dec 05 2014

LINKS

Colin Barker, Table of n, a(n) for n = 1..436

Index entries for linear recurrences with constant coefficients, signature (1,39202,-39202,-1,1).

FORMULA

G.f.: 2*x^2*(6*x^3+2885*x^2-6726*x-85) / ((x-1)*(x^2-198*x+1)*(x^2+198*x+1)). - Colin Barker, Dec 05 2014

PROG

(PARI) concat(0, Vec(2*x^2*(6*x^3+2885*x^2-6726*x-85)/((x-1)*(x^2-198*x+1)*(x^2+198*x+1)) + O(x^100))) \\ Colin Barker, Dec 05 2014

CROSSREFS

Cf. A133324, A133327.

Sequence in context: A187520 A210784 A178499 * A098244 A250957 A114048

Adjacent sequences:  A133325 A133326 A133327 * A133329 A133330 A133331

KEYWORD

nonn,easy

AUTHOR

Richard Choulet, Oct 18 2007

EXTENSIONS

More terms from Colin Barker, Dec 05 2014

STATUS

approved

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Last modified June 27 19:17 EDT 2022. Contains 354897 sequences. (Running on oeis4.)