login
This site is supported by donations to The OEIS Foundation.

 

Logo

Please make a donation to keep the OEIS running. We are now in our 55th year. In the past year we added 12000 new sequences and reached 8000 citations (which often say "discovered thanks to the OEIS"). We need to raise money to hire someone to manage submissions, which would reduce the load on our editors and speed up editing.
Other ways to donate

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A252076 Numbers n such that the sum of the heptagonal numbers H(n) and H(n+1) is equal to the hexagonal number X(m) for some m. 2
0, 486, 701100, 1010986002, 1457841114072, 2102205875506110, 3031379414638696836, 4371247013703125331690, 6303335162380492089600432, 9089404932905655890078491542, 13106915609914793413001095203420, 18900163220092199195891689204840386 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Also nonnegative integers x in the solutions to 10*x^2-4*y^2+4*x+2*y+2 = 0, the corresponding values of y being A252077.

LINKS

Colin Barker, Table of n, a(n) for n = 1..317

Index entries for linear recurrences with constant coefficients, signature (1443,-1443,1).

FORMULA

a(n) = 1443*a(n-1)-1443*a(n-2)+a(n-3).

G.f.: 18*x^2*(11*x-27) / ((x-1)*(x^2-1442*x+1)).

EXAMPLE

486 is in the sequence because H(486)+H(487) = 589761+592192 = 1181953 = X(769).

MATHEMATICA

LinearRecurrence[{1443, -1443, 1}, {0, 486, 701100}, 20] (* Harvey P. Dale, Oct 13 2015 *)

PROG

(PARI) concat(0, Vec(18*x^2*(11*x-27)/((x-1)*(x^2-1442*x+1)) + O(x^100)))

CROSSREFS

Cf. A000384, A000566, A252077.

Sequence in context: A223412 A097765 A179428 * A178813 A178814 A178812

Adjacent sequences:  A252073 A252074 A252075 * A252077 A252078 A252079

KEYWORD

nonn,easy

AUTHOR

Colin Barker, Dec 13 2014

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.

License Agreements, Terms of Use, Privacy Policy. .

Last modified December 10 12:30 EST 2019. Contains 329895 sequences. (Running on oeis4.)