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A338495 Least number of hexagonal pyramidal numbers needed to represent n.

%I A338495 #8 Feb 16 2025 08:34:00
%S A338495 1,2,3,4,5,6,1,2,3,4,5,6,7,2,3,4,5,6,7,8,3,1,2,3,4,5,6,4,2,3,4,5,6,7,
%T A338495 5,3,4,5,6,7,8,6,4,2,3,4,5,6,7,1,2,3,4,5,6,7,2,3,4,5,6,7,8,3,4,3,4,5,
%U A338495 6,7,4,2,3,4,5,6,7,5,3,4,5,6,7,8,6,4,5,4,5,6,7,7,5,3,1,2,3,4,5,2,3
%N A338495 Least number of hexagonal pyramidal numbers needed to represent n.
%H A338495 Robert Israel, <a href="/A338495/b338495.txt">Table of n, a(n) for n = 1..10000</a>
%H A338495 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/HexagonalPyramidalNumber.html">Hexagonal Pyramidal Number</a>
%H A338495 <a href="/index/Ps#pyramidal_numbers">Index to sequences related to pyramidal numbers</a>
%p A338495 N:= 200: # for a(1)..a(N)
%p A338495 V:= Vector(N):
%p A338495 S:= {seq(n*(n+1)*(4*n-1)/6,n=1..floor((N*3/2)^(1/3)))}:
%p A338495 V[convert(S,list)]:= 1:
%p A338495 T:= S:
%p A338495 for m from 2 do
%p A338495   Tn:= select(`<=`,map(t -> op(t +~ S),T),N) minus T;
%p A338495   if nops(Tn) = 0 then break fi;
%p A338495   T:= T union Tn;
%p A338495   V[convert(Tn,list)]:= m
%p A338495 od:
%p A338495 convert(V,list); # _Robert Israel_, Nov 02 2020
%Y A338495 Cf. A002412, A104246, A234533, A338479, A338493, A338494.
%K A338495 nonn
%O A338495 1,2
%A A338495 _Ilya Gutkovskiy_, Oct 30 2020