%I A066370
%S A066370 0,1,231,26796,1186570,26357430,359026206,3413156131,24666759216,
%T A066370 143717956515,703974775735,2989908659661,11270904497931,38398515291136,
%U A066370 119929709686710,347357071281165,941718655098991,2408309883851256
%N A066370 Quadruply triangular numbers.
%C A066370 See sequences A000217, A002817 and A064322 for triangular, doubly triangular 
               and triply triangular numbers, respectively.
%F A066370 a(n) = n*(n + 1)*(n^2 + n + 2)*(n^4 + 2*n^3 + 3*n^2 + 2*n + 8)*(n^8 + 
               4*n^7 + 10*n^6 + 16*n^5 + 25*n^4 + 28*n^3 + 28*n^2 + 16*n + 128)/
               32768.
%F A066370 a(n) = A064322(n)*(A064322(n) + 1)/2 = A000217(A000217(A000217(A000217(n))))
%e A066370 a(2)=231 as A000217(A000217(A000217(A000217(2))))=231 is the second quadruply-triangular 
               number.
%t A066370 f[n_] := n(n + 1)/2; Table[ Nest[f, n, 4], {n, 0, 17}] (from Robert G. 
               Wilson v Jun 30 2004)
%Y A066370 Sequence in context: A029569 A152102 A152500 this_sequence A139412 A027551 
               A068750
%Y A066370 Adjacent sequences: A066367 A066368 A066369 this_sequence A066371 A066372 
               A066373
%K A066370 nonn
%O A066370 0,3
%A A066370 Brian Bayerle (bbayer03(AT)providence.edu), Dec 22 2001