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A120454 a(n) = ceiling(GPF(n)/LPF(n)) where GPF is greatest prime factor, LPF is least prime factor. 2
1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 1, 2, 1, 4, 2, 1, 1, 2, 1, 3, 3, 6, 1, 2, 1, 7, 1, 4, 1, 3, 1, 1, 4, 9, 2, 2, 1, 10, 5, 3, 1, 4, 1, 6, 2, 12, 1, 2, 1, 3, 6, 7, 1, 2, 3, 4, 7, 15, 1, 3, 1, 16, 3, 1, 3, 6, 1, 9, 8, 4, 1, 2, 1, 19, 2, 10, 2, 7, 1, 3, 1, 21, 1, 4, 4, 22, 10, 6, 1, 3, 2, 12, 11, 24, 4, 2, 1, 4, 4 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,6

COMMENTS

Given GPF(n) and LPF(n), the sum is A074320, the difference is A046665 and the product is A066048. a(n) = 1 iff n is p^k iff n is in A000961.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

FORMULA

a(n) = ceiling(A006530(n)/A020639(n)).

EXAMPLE

a(26) = ceiling(GPF(26)/LPF(26)) = ceiling(13/2) = 7.

MAPLE

A120454 := proc(n) local ifs ; if n = 1 then RETURN(1) ; else ifs := ifactors(n)[2] ; RETURN( ceil(op(1, op(-1, ifs))/op(1, op(1, ifs))) ) ; fi ; end ; for n from 1 to 100 do printf("%d, ", A120454(n)) ; od ; # R. J. Mathar, Dec 16 2006

PROG

(PARI) A120454(n) = if(1==n, 1, my(f = factor(n), lpf = f[1, 1], gpf = f[#f~, 1]); ceil(gpf/lpf)); \\ Antti Karttunen, Sep 06 2018

CROSSREFS

Cf. A000040, A006530, A020639, A074320, A046665, A066048.

Sequence in context: A032436 A280274 A073408 * A321648 A330755 A316431

Adjacent sequences: A120451 A120452 A120453 * A120455 A120456 A120457

KEYWORD

easy,nonn

AUTHOR

Jonathan Vos Post, Aug 16 2006

EXTENSIONS

Corrected and extended by R. J. Mathar, Dec 16 2006

STATUS

approved

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Last modified November 26 17:30 EST 2022. Contains 358362 sequences. (Running on oeis4.)