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A074238 Numbers n such that the sum of the reverses of 1,2,...,n is a perfect square. 0
1, 8, 26, 53, 3087, 6173, 8091, 12330, 18358, 42898, 294847, 27382381, 49290155, 426131190, 1350661780, 3161620702, 4461944219, 17625479383, 40766706170, 61554358125, 270930998357 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

a(22) > 5*10^11. - Giovanni Resta, Apr 16 2017

LINKS

Table of n, a(n) for n=1..21.

EXAMPLE

reverse(1) + reverse(2) + ... + reverse(25) + reverse(26) = 1 + 2 + ...+ 52 + 62 = 729 = 27^2, so 26 is a term of the sequence.

MATHEMATICA

s = 0; r = {}; For[i = 1, i <= 10^5, i++, s = s + FromDigits[Reverse[IntegerDigits[i]]]; If[IntegerQ[s^(1/2)], r = Append[r, i]]]; r

CROSSREFS

Cf. A062918.

Sequence in context: A143894 A126176 A240754 * A126264 A225274 A085690

Adjacent sequences:  A074235 A074236 A074237 * A074239 A074240 A074241

KEYWORD

base,nonn

AUTHOR

Joseph L. Pe, Sep 19 2002

EXTENSIONS

a(11)-a(21) from Giovanni Resta, Apr 16 2017

STATUS

approved

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Last modified April 21 06:10 EDT 2021. Contains 343146 sequences. (Running on oeis4.)