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A094890
Triangular numbers whose sum of squared digits is also triangular.
1
0, 1, 6, 10, 36, 630, 741, 1081, 2211, 7140, 10011, 10153, 13366, 15576, 17766, 23220, 24531, 25651, 28920, 33411, 42486, 47586, 52326, 59685, 61776, 69006, 112575, 113050, 121771, 125751, 128778, 129286, 146611, 156520, 163306, 165025, 167331
OFFSET
1,3
LINKS
MAPLE
isA094890 := proc(n)
if isA000217(n) and isA000217(A003132(n)) then
true;
else
false;
end if;
end proc:
for n from 0 to 300 do
T := A000217(n) ;
if isA094890(T) then
printf("%d, ", T) ;
end if;
end do: # R. J. Mathar, Nov 15 2019
MATHEMATICA
tri[n_] := n (n + 1)/2; triQ[n_] := IntegerQ @ Sqrt[8 n + 1]; sumSqDig[n_] := Total @ (IntegerDigits[n]^2); aQ[n_] := triQ @ sumSqDig @ tri[n]; tri /@ Select[Range[0, 578], aQ] (* Amiram Eldar, Dec 23 2019 *)
CROSSREFS
Cf. A003132.
Sequence in context: A221519 A332984 A038264 * A213477 A047178 A132095
KEYWORD
base,nonn
AUTHOR
Jason Earls, Jun 16 2004
STATUS
approved