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A254005 Numbers that divide the reverse of the sum of their aliquot parts. 2
1, 6, 2274, 44304, 229974, 498906, 4177662, 20671542, 22999974, 41673714, 73687923, 403999652, 479444901, 4158499614, 27378395352, 209659386726, 216276435966, 229999999974, 406406685462, 922964834547 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Noting 2274, 229974, and 22999974, 23*10^n-26 is a term herein for any n in A253968. - Hans Havermann, Jan 24 2015

Additionally, 404*10^(6*n)-348 is a term herein if this is 28 times a prime. Three such numbers are known: n = 1, 10, and 1608. - Hans Havermann, Jan 28 2015

a(21) > 10^12. - Giovanni Resta, May 09 2015

LINKS

Table of n, a(n) for n=1..20.

EXAMPLE

sigma(1) - 1 = 0, Rev(0) = 0 and 0 / 1 = 0.

sigma(6) - 6 = 6, Rev(6) = 6 and 6 / 6 = 1.

sigma(2274) - 2274 = 2286, Rev(2286) = 6822 and 6822 / 2274 = 3.

MAPLE

with(numtheory): T:=proc(w) local x, y, z; x:=w; y:=0;

for z from 1 to ilog10(x)+1 do y:=10*y+(x mod 10); x:=trunc(x/10);

od; y; end:

P:=proc(q) local n; for n from 1 to q do

if type(T(sigma(n)-n)/n, integer) then print(n);

fi; od; end: P(10^9);

MATHEMATICA

fQ[n_] := Mod[ FromDigits@ Reverse@ IntegerDigits[ DivisorSigma[1, n] - n], n] == 0; k = 1; lst = {}; While[k < 1000000001, If[fQ@ k, AppendTo[lst, k]]; k++]; lst (* Robert G. Wilson v, Jan 28 2015 *)

PROG

(PARI) rev(n) = subst(Polrev(digits(n)), x, 10);

isok(n) = rev(sigma(n)-n) % n == 0; \\ Michel Marcus, Jan 25 2015

(MAGMA) [n: n in [1..10^7] | Seqint(Reverse(Intseq(SumOfDivisors(n)-n))) mod n eq 0]; // Vincenzo Librandi, May 09 2015

CROSSREFS

Cf. A000203, A001065, A253968, A254004.

Sequence in context: A067174 A153300 A059203 * A279654 A198403 A279533

Adjacent sequences:  A254002 A254003 A254004 * A254006 A254007 A254008

KEYWORD

nonn,base,more

AUTHOR

Paolo P. Lava, Jan 22 2015

EXTENSIONS

More terms from Hans Havermann, Jan 24 2015

a(13) from Robert G. Wilson v, Jan 29 2015

a(14)-a(20) from Giovanni Resta, May 09 2015

STATUS

approved

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Last modified August 17 18:38 EDT 2017. Contains 290655 sequences.