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%I #10 Mar 31 2012 13:48:25
%S 5,23,51,71,72,99,123,239,263,311,359,479,599,699,743,863,911,1031,
%T 1103,1151,1431,1563,1583,1823,1851,1863,2111,2543,2663,3023,3119,
%U 3191,3291,3671,3719,3863,4131,4203,4271,4463,4671,4703,5039,5231,5351,5391,5399
%N Terms in A136112 which are not in A135768.
%C Pentagonal-Indices of terms in A136113 which are not in A135769.
%C A135768 resp. A135769 are subsequences of A136112 resp. A136113; the present sequence gives the indices of the elements of the former which are not in the latter: A136113(A135771(k)), k=1,2,3,... are the pentagonal numbers P(m) which are not the difference of two pentagonal numbers P(n)-P(q) with n,q>m, but only with n>m>q. A136112(A135771(k)) are the corresponding indices of the pentagonal numbers.
%H Donovan Johnson, <a href="/A135771/b135771.txt">Table of n, a(n) for n = 1..200</a>
%F Equals the difference set A136112 \ A135768.
%e The first terms of this sequence correspond to the following elements of A136113:
%e P_5 = P_7 - P_5,
%e P_23 = P_24 - P_7,
%e P_51 = P_66 - P_42,
%e P_71 = P_74 - P_21,
%e P_72 = P_80 - P_35,
%e P_99 = P_104 - P_32,
%e P_123 = P_144 - P_75,
%e P_239 = P_249 - P_70,
%e P_263 = P_274 - P_77,
%e P_311 = P_324 - P_91,
%e P_359 = P_374 - P_10.
%o (PARI) P(n)=n*(3*n-1)/2
%o isPent(t)=P(sqrtint((t*2)\3)+1)==t
%o {for( i=1,999, for( j=1,i-1, isPent(P(i)+P(j))|next; for( k=i+1,(P(i)-1)\3, isPent(P(i)+P(k))&next(3)); print1(i", "); next(2)))}
%Y Cf. A000326, A136112-A136118, A135768-A135769.
%K nonn
%O 1,1
%A _R. J. Mathar_ and _M. F. Hasler_, Feb 07 2008
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