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 A245644 Numbers n such that n^3 is an arithmetic number. 2
 1, 3, 5, 7, 11, 13, 14, 15, 17, 19, 21, 23, 24, 29, 31, 33, 35, 37, 39, 41, 42, 43, 46, 47, 51, 52, 53, 55, 56, 57, 59, 61, 62, 65, 66, 67, 69, 70, 71, 73, 77, 79, 80, 83, 85, 87, 89, 91, 93, 94, 95, 97, 101, 103, 105, 107, 109, 111, 113, 114, 115, 117, 119, 120, 123, 127, 129, 131, 133, 137, 138, 139 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS A065091 is a subsequence. LINKS Reinhard Zumkeller and Jens Kruse Andersen, Table of n, a(n) for n = 1..10000 (first 147 terms from Reinhard Zumkeller) Wikipedia, Arithmetic number FORMULA A245656(a(n)^3) = 1. - Reinhard Zumkeller, Jul 28 2014 MAPLE isArithPow := proc(n, e)     local dvs, d ;     dvs := numtheory[divisors](n^e) ;     add(d, d=dvs)/nops(dvs) ;     if type(%, 'integer') then         true;     else         false;     end if; end proc: for n to 300 do     if isArithPow(n, 3) then         printf("%d, ", n) ;     end if; end do: MATHEMATICA Select[Range[120], IntegerQ[DivisorSigma[1, #^3 ]/DivisorSigma[0, #^3 ]] &] (* Michael De Vlieger, Aug 05 2014 after Stefan Steinerberger at A003601 *) PROG (Haskell) a245644 n = a245644_list !! (n-1) a245644_list = filter ((== 1) . a245656 . (^ 3)) [1..] -- Reinhard Zumkeller, Jul 28 2014 (Python) from sympy import divisors, divisor_count [n for n in range(1, 10**3) if not sum(divisors(n**3)) % divisor_count(n**3)] # Chai Wah Wu, Aug 04 2014 CROSSREFS Cf. A003601, A107924, A107925. Cf. A245656. Sequence in context: A285848 A086527 A161554 * A070087 A100933 A325128 Adjacent sequences:  A245641 A245642 A245643 * A245645 A245646 A245647 KEYWORD nonn AUTHOR R. J. Mathar, Jul 28 2014 STATUS approved

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Last modified October 15 13:06 EDT 2019. Contains 328030 sequences. (Running on oeis4.)