A069672 Largest n-digit triangular number with minimum digit sum.
1, 10, 300, 3003, 20100, 112101, 2001000, 33020001, 200010000, 3200120001, 20000100000, 320001200001, 2000001000000, 32000012000001, 200000010000000, 3200000120000001, 20000000100000000, 320000001200000001, 2000000001000000000, 32000000012000000001, 200000000010000000000, 3200000000120000000001, 20000000000100000000000, 320000000001200000000001, 2000000000001000000000000, 32000000000012000000000001, 200000000000010000000000000, 3200000000000120000000000001, 20000000000000100000000000000, 320000000000001200000000000001
Offset: 1
Crossrefs
Programs
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Maple
F:= proc(d) local s, P, nP, S, x, bestx; bestx:= 0; for s in [1,3,6,9] do for P in map(op @combinat:-permute, combinat:-partition(s)) do nP:= nops(P); for S in map(t -> [d-1, op(t)], combinat:-choose([$0..d-2],nP-1)) do x:= add(P[i]*10^S[i],i=1..nP); if x > bestx and issqr(1+8*x) then bestx:= x fi; od; od; if bestx > 0 then return bestx fi; od; end proc: seq(F(d),d=1..30); # Robert Israel, May 25 2016
Extensions
More terms from Vladeta Jovovic, Apr 07 2002
a(15)..a(30) from Robert Israel, May 25 2016
Comments