login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A072194 Replace all prime factors p of n with n-p. 1
1, 0, 0, 4, 0, 12, 0, 216, 36, 40, 0, 900, 0, 84, 120, 38416, 0, 3600, 0, 4860, 252, 220, 0, 223608, 400, 312, 13824, 14196, 0, 18900, 0, 24300000, 660, 544, 840, 1258884, 0, 684, 936, 1920520, 0, 54600, 0, 58212, 70560, 1012, 0, 201485520, 1764, 97200 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

a(n)=0 iff n is prime.

LINKS

Paolo P. Lava, Table of n, a(n) for n = 1..10000

EXAMPLE

a(18) = a(2*3*3) = (18-2)*(18-3)*(18-3) = 16*15*15 = 3600.

MAPLE

with(numtheory): P:=proc(n) local p; mul((n-op(1, p))^op(2, p), p=ifactors(n)[2]); end: seq(P(i), i=1..50); # Paolo P. Lava, Mar 22 2018

MATHEMATICA

Join[{1}, Table[Times@@(n-#&/@Flatten[Table[#[[1]], #[[2]]]&/@FactorInteger[ n]]), {n, 2, 50}]] (* Harvey P. Dale, Dec 04 2018 *)

PROG

(PARI) a(n) = {my(f = factor(n)); for (k=1, #f~, f[k, 1] = n - f[k, 1]; ); factorback(f); } \\ Michel Marcus, Mar 22 2018

CROSSREFS

Sequence in context: A167296 A147607 A174087 * A225952 A273795 A273858

Adjacent sequences:  A072191 A072192 A072193 * A072195 A072196 A072197

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jul 02 2002

STATUS

approved

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

License Agreements, Terms of Use, Privacy Policy. .

Last modified July 28 14:19 EDT 2021. Contains 346335 sequences. (Running on oeis4.)