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%I A145172 #9 Apr 22 2021 04:07:21
%S A145172 1,2,3,4,1,2,3,4,5,2,3,1,2,3,4,5,2,3,4,5,6,1,2,3,4,5,2,3,4,5,6,3,4,2,
%T A145172 1,2,3,4,5,2,3,4,5,6,3,4,2,3,4,5,1,2,3,4,5,2,3,4,5,6,3,4,2,3,4,5,6,3,
%U A145172 4,1,2,3,4,5,2,3,4,5,6,3,4,2,3,4,5,6,3,4,5,6
%N A145172 Number of pentagonal numbers needed to represent n with greedy algorithm.
%C A145172 Sequence is unbounded.
%H A145172 Andrew Howroyd, <a href="/A145172/b145172.txt">Table of n, a(n) for n = 1..10000</a>
%e A145172 a(21)=6 since 21 = 12+5+1+1+1+1.
%o A145172 (PARI) a(n)={my(s=0); forstep(k=(sqrtint(24*n+1)+1)\6, 1, -1, my(t=k*(3*k-1)/2); s+=n\t; n%=t); s} \\ _Andrew Howroyd_, Apr 21 2021
%Y A145172 Cf. A000326 (pentagonal numbers), A053610, A057945, A180447, A192988.
%K A145172 nonn
%O A145172 1,2
%A A145172 Christina Steffan (christina.steffan(AT)gmx.at), Oct 03 2008
%E A145172 Terms a(41) and beyond from _Andrew Howroyd_, Apr 21 2021

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