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

1,2

Comments

Does the obvious pattern continue? - Vladeta Jovovic, Apr 07 2002

Links

Table of n, a(n) for n=1..30.

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

Crossrefs

Cf. A069661, A069662, A069663, A069664, A069665, A069666, A069667, A069668, A069669, A069670, A069671.

Sequence in context: A217487 A173479 A173478 * A129005 A162729 A278037

Adjacent sequences: A069669 A069670 A069671 * A069673 A069674 A069675

Keyword

nonn,base

Author

Amarnath Murthy, Apr 06 2002

Extensions

More terms from Vladeta Jovovic, Apr 07 2002

a(15)..a(30) from Robert Israel, May 25 2016

Status

approved