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

 

Logo

Annual Appeal: Today, Nov 11 2014, is the 4th anniversary of the launch of the new OEIS web site. 70,000 sequences have been added in these four years, all edited by volunteers. Please make a donation (tax deductible in the US) to help keep the OEIS running.

Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A172437 Indices of pentagonal pyramidal numbers which are the sum of two other such numbers: k such that A002411(k) = A002411(i)+A002411(j) for some i,j>0. 2

%I

%S 42,82,171,411,522,886,1042,1066,1183,1341,2596,2842,3480,3831,5012,

%T 5316,5360,5786,6219,6650,6924,8406,8666,9408,10707,11735,12590,12891,

%U 14422,14646,14826,17351,17702,17757,18882,23210,24108,25127,28175,31980,32400

%N Indices of pentagonal pyramidal numbers which are the sum of two other such numbers: k such that A002411(k) = A002411(i)+A002411(j) for some i,j>0.

%C The numbers themselves are listed in A172425. This answers a question posed in A133459.

%H Donovan Johnson, <a href="/A172437/b172437.txt">Table of n, a(n) for n = 1..160</a>

%e a(1)=42 because A002411(42) is the smallest term in that sequence which is the sum of two other (nonzero) terms of A002411.

%o (Pari) for(n=1,99999,for(m=1,n-1, isA002411(p(n)-p(m)) & !print1(n", ") & break)) /* needs isA002411() and p() */

%Y Cf. A133459, A172425.

%K nonn

%O 1,1

%A _M. F. Hasler_, Nov 20 2010

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

Content is available under The OEIS End-User License Agreement .

Last modified December 21 01:10 EST 2014. Contains 252291 sequences.