The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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 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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 24 21:35 EDT 2020. Contains 337322 sequences. (Running on oeis4.)