The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A303994 Numbers whose sum of divisors is the fourth power of one of their divisors. 7
 1, 510, 642, 3394440, 3629640, 3653640, 3663240, 3673080, 3701160, 3736920, 3901080, 3958680, 4077960, 4137240, 4240920, 4251480, 4256520, 4273320, 4274520, 4319880, 7300854, 12798240, 13362720, 14405664, 15170820, 16173024, 16342368, 16354884, 16361184, 16957668, 17113404 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS Subset of A019422. LINKS Giovanni Resta, Table of n, a(n) for n = 1..1565 (terms < 10^12; first 398 terms from Robert Israel) EXAMPLE Divisors of 510 are 1, 2, 3, 5, 6, 10, 15, 17, 30, 34, 51, 85, 102, 170, 255, 510 and their sum is 1296 = 6^4. MAPLE with(numtheory): P:=proc(q) local a, k, n; for n from 1 to q do a:=sort([op(divisors(n))]); for k from 1 to nops(a) do if sigma(n)=a[k]^4 then print(n); break; fi; od; od; end: P(10^9); MATHEMATICA Select[Range[17114000], MemberQ[Divisors[#]^4, DivisorSigma[1, #]]&] (* Harvey P. Dale, Jul 22 2021 *) PROG (PARI) isok(n) = (n==1) || (ispower(s=sigma(n), 4) && !(n % sqrtnint(s, 4))); \\ Michel Marcus, May 05 2018 CROSSREFS Cf. A000203, A019422, A303123, A303993, A303995, A303996. Sequence in context: A071687 A345361 A048254 * A249551 A248790 A252877 Adjacent sequences: A303991 A303992 A303993 * A303995 A303996 A303997 KEYWORD nonn AUTHOR Paolo P. Lava, May 04 2018 EXTENSIONS More terms from Michel Marcus, May 05 2018 STATUS approved

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

Last modified March 2 07:45 EST 2024. Contains 370460 sequences. (Running on oeis4.)