cp's OEIS Frontend

This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.

A049599 Number of (1+e)-divisors of n: if n = Product p(i)^r(i), d = Product p(i)^s(i) and s(i) = 0 or s(i) divides r(i), then d is a (1+e)-divisor of n.

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%I A049599 #32 Feb 26 2024 01:25:22
%S A049599 1,2,2,3,2,4,2,3,3,4,2,6,2,4,4,4,2,6,2,6,4,4,2,6,3,4,3,6,2,8,2,3,4,4,
%T A049599 4,9,2,4,4,6,2,8,2,6,6,4,2,8,3,6,4,6,2,6,4,6,4,4,2,12,2,4,6,5,4,8,2,6,
%U A049599 4,8,2,9,2,4,6,6,4,8,2,8,4,4,2,12,4,4,4,6,2,12,4,6,4,4,4,6,2,6,6,9,2,8,2
%N A049599 Number of (1+e)-divisors of n: if n = Product p(i)^r(i), d = Product p(i)^s(i) and s(i) = 0 or s(i) divides r(i), then d is a (1+e)-divisor of n.
%C A049599 A divisor of n is a (1+e)-divisor if and only if it is a unitary divisor of an exponential divisor of n (see A077610 and A322791). - _Amiram Eldar_, Feb 26 2024
%H A049599 Reinhard Zumkeller, <a href="/A049599/b049599.txt">Table of n, a(n) for n = 1..10000</a>
%F A049599 If n = Product p(i)^r(i) then a(n) = Product (tau(r(i))+1), where tau(n) = number of divisors of n, cf. A000005. - _Vladeta Jovovic_, Apr 29 2001
%t A049599 a[n_] := Times @@ (DivisorSigma[0, #] + 1 &)  /@ FactorInteger[n][[All, 2]]; a[1] = 1; Table[a[n], {n, 1, 103}] (* _Jean-François Alcover_, Oct 10 2011 *)
%o A049599 (Haskell)
%o A049599 a049599 = product . map ((+ 1) . a000005 . fromIntegral) . a124010_row
%o A049599 -- _Reinhard Zumkeller_, Mar 13 2012
%o A049599 (PARI) a(n) = vecprod(apply(x->numdiv(x)+1, factor(n)[, 2])); \\ _Amiram Eldar_, Aug 13 2023
%Y A049599 Cf. A049603, A051378.
%Y A049599 Cf. A124010, A000005, A049419, A077610, A322791.
%K A049599 nonn,easy,nice,mult
%O A049599 1,2
%A A049599 _Yasutoshi Kohmoto_
%E A049599 More terms from _Naohiro Nomoto_, Apr 12 2001