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

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A117082 Octagonal numbers for which the sum of the digits is also a octagonal number. 1

%I

%S 0,1,8,341,1160,4485,6816,9633,12936,16725,20501,25761,30401,36741,

%T 42960,64533,81345,90480,131880,143445,168033,181056,208560,238008,

%U 253461,269400,302736,338016,375240,414408,434721,455520,520833,590520

%N Octagonal numbers for which the sum of the digits is also a octagonal number.

%H Harvey P. Dale, <a href="/A117082/b117082.txt">Table of n, a(n) for n = 0..1000</a>

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

%t 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 *)

%t 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 *)

%Y Cf. A000567.

%K base,nonn

%O 0,3

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

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 May 7 23:48 EDT 2021. Contains 343652 sequences. (Running on oeis4.)