The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A254228 Indices of heptagonal numbers (A000566) which are also centered square numbers (A001844). 3
 1, 41, 185, 13105, 59473, 4219673, 19150025, 1358721505, 6166248481, 437504104841, 1985512860761, 140874963037201, 639328974916465, 45361300593873785, 205861944410240873, 14606197916264321473, 66286906771122644545, 4703150367736517640425 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Also positive integers x in the solutions to 5*x^2 - 4*y^2 - 3*x + 4*y - 2 = 0, the corresponding values of y being A254229. LINKS Colin Barker, Table of n, a(n) for n = 1..797 Index entries for linear recurrences with constant coefficients, signature (1,322,-322,-1,1). FORMULA a(n) = a(n-1)+322*a(n-2)-322*a(n-3)-a(n-4)+a(n-5). G.f.: -x*(x^4+40*x^3-178*x^2+40*x+1) / ((x-1)*(x^2-18*x+1)*(x^2+18*x+1)). EXAMPLE 41 is in the sequence because the 41st heptagonal number is 4141, which is also the 46th centered square number. PROG (PARI) Vec(-x*(x^4+40*x^3-178*x^2+40*x+1)/((x-1)*(x^2-18*x+1)*(x^2+18*x+1)) + O(x^100)) CROSSREFS Cf. A000566, A001844, A254229, A254230. Sequence in context: A282941 A141922 A142080 * A141939 A264653 A297227 Adjacent sequences:  A254225 A254226 A254227 * A254229 A254230 A254231 KEYWORD nonn,easy AUTHOR Colin Barker, Jan 27 2015 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified July 31 10:51 EDT 2021. Contains 346373 sequences. (Running on oeis4.)