A117082 Octagonal numbers for which the sum of the digits is also an octagonal number.

0, 1, 8, 341, 1160, 4485, 6816, 9633, 12936, 16725, 20501, 25761, 30401, 36741, 42960, 64533, 81345, 90480, 131880, 143445, 168033, 181056, 208560, 238008, 253461, 269400, 302736, 338016, 375240, 414408, 434721, 455520, 520833, 590520

Offset

0,3

Links

Harvey P. Dale, Table of n, a(n) for n = 0..1000

Example

1160 is in the sequence because (1) it is an octagonal number and (2)the sum of its digits 1+1+6+0=8 is also an octagonal number.

Mathematica

octQ[n_] := IntegerQ[(Sqrt[3 n + 1] + 1)/3]; t = {0}; Do[x = n*(3 n - 2); If[octQ[Plus @@ IntegerDigits[x]], AppendTo[t, x]], {n, 450}]; t (* Jayanta Basu, Jul 13 2013 *)
With[{oct=PolygonalNumber[8, Range[0, 500]]}, Select[oct, MemberQ[oct, Total[ IntegerDigits[ #]]]&]] (* The program uses the PolygonalNumber function from Mathematica version 10 *) (* Harvey P. Dale, Mar 06 2016 *)

Crossrefs

Cf. A000567.

Sequence in context: A258745 A071306 A214511 * A061458 A135067 A002781

Adjacent sequences: A117079 A117080 A117081 * A117083 A117084 A117085

Keyword

base,nonn

Author

Luc Stevens (lms022(AT)yahoo.com), Apr 17 2006

Status

approved