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A113654 Numbers n such that the square of n contains sigma(n) as a substring, in base 10. 0
1, 11, 101, 125, 153, 1205, 1502, 1810, 3080, 7631, 18010, 18650, 21020, 36559, 36911, 44805, 53999, 60541, 68443, 120005, 189585, 210020, 487195, 1059449, 1750004, 1800010, 1860050, 1872250, 2072139, 2170100, 2268661, 2496750 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

If p=180...01 is prime, then n=2*5*p=180...010, n^2=3240...0360...0100 and sigma(n)=3240...036, thus n belongs to the sequence.

LINKS

Table of n, a(n) for n=1..32.

EXAMPLE

153^2=23409 and sigma(153)=234.

MATHEMATICA

lst = {}; Do[If[{}!= StringPosition[ToString[n^2], ToString@DivisorSigma[1, n]], AppendTo[lst, n]], {n, 10^6}]; lst

CROSSREFS

Sequence in context: A303570 A208262 A062696 * A066592 A316604 A208362

Adjacent sequences:  A113651 A113652 A113653 * A113655 A113656 A113657

KEYWORD

base,nonn

AUTHOR

Giovanni Resta, Jan 26 2006

STATUS

approved

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Last modified October 17 04:09 EDT 2019. Contains 328106 sequences. (Running on oeis4.)