A281686 - OEIS

A281686

Numbers k such that A001222(k) = A001222(A003415(k)).

4, 8, 9, 14, 21, 25, 26, 27, 32, 33, 36, 38, 46, 48, 49, 50, 54, 57, 62, 69, 74, 80, 85, 88, 93, 94, 99, 100, 106, 121, 125, 128, 129, 133, 134, 145, 156, 166, 169, 176, 177, 178, 205, 207, 213, 216, 217, 218, 226, 230, 237, 240, 242, 243, 248, 249, 252, 253

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OFFSET

1,1

COMMENTS

Numbers k such that the number of prime divisors (counted with multiplicity) of k is equal to the number of prime divisors (counted with multiplicity) of the arithmetic derivative of k.

LINKS

Colin Barker, Table of n, a(n) for n = 1..1000

PROG

(PARI) arde(n) = sum(i=1, #f=factor(n)~, n/f[1, i]*f[2, i])

select(k->bigomega(k)==bigomega(arde(k)), vector(400, k, k+1))

CROSSREFS

Cf. A001222, A003415, A209870, A281685.

Sequence in context: A312831 A085711 A182491 * A122785 A280450 A137055

Adjacent sequences: A281683 A281684 A281685 * A281687 A281688 A281689

KEYWORD

nonn

AUTHOR

Colin Barker, Jan 27 2017

STATUS

approved