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A240895 Consider a number of k digits n = d_(k)*10^(k-1) + d_(k-1)*10^(k-2) + … + d_(2)*10 + d_(1). Sequence lists the numbers n such that sigma(n) - n = Sum_{i=1..k-1}{sigma(Sum_{j=1..i}{d_(j)*10^(j-1)})}} (see example below). 2
11, 25, 31, 41, 61, 71, 341, 671, 2119, 10231, 39579, 52231, 60341, 402959, 1288689, 1393059, 1956759, 16752951, 108659999, 181704519, 794033191, 1062726071, 3518397571, 4062296851, 4085227151, 7015608139 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

a(27) > 10^10. - Giovanni Resta, Apr 16 2014

LINKS

Table of n, a(n) for n=1..26.

EXAMPLE

If n = 52231, starting from the least significant digit, let us cut the number into the set 1, 31, 231, 2231. We have:

sigma(1) = 1;

sigma(31) = 32;

sigma(231) = 384;

sigma(2231) = 2352

and 1 + 32 + 384 + 2352 = 2769 = sigma(52231) - 52231.

MAPLE

with(numtheory); P:=proc(q) local a, k, n;

for n from 2 to q do a:=0; k:=1; while (n mod 10^k)<n do

a:=a+sigma(n mod 10^k); k:=k+1; od;

if sigma(n)-n=a then print(n); fi; od; end: P(10^9);

CROSSREFS

Cf. A000203, A240894, A240896-A240902.

Sequence in context: A251412 A286279 A125868 * A301635 A031025 A140675

Adjacent sequences:  A240892 A240893 A240894 * A240896 A240897 A240898

KEYWORD

nonn,more,base

AUTHOR

Paolo P. Lava, Apr 14 2014

EXTENSIONS

a(14), a(18)-a(26) from Giovanni Resta, Apr 16 2014

STATUS

approved

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Last modified December 9 02:53 EST 2021. Contains 349625 sequences. (Running on oeis4.)