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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

Amiram Eldar, Table of n, a(n) for n = 1..10000

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

Adjacent sequences:  A094887 A094888 A094889 * A094891 A094892 A094893

KEYWORD

base,nonn

AUTHOR

Jason Earls, Jun 16 2004

STATUS

approved

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Last modified July 15 15:15 EDT 2020. Contains 335774 sequences. (Running on oeis4.)