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A072438 Remove prime factors of form 4*k+1. 2
1, 2, 3, 4, 1, 6, 7, 8, 9, 2, 11, 12, 1, 14, 3, 16, 1, 18, 19, 4, 21, 22, 23, 24, 1, 2, 27, 28, 1, 6, 31, 32, 33, 2, 7, 36, 1, 38, 3, 8, 1, 42, 43, 44, 9, 46, 47, 48, 49, 2, 3, 4, 1, 54, 11, 56, 57, 2, 59, 12, 1, 62, 63, 64, 1, 66, 67, 4, 69, 14, 71, 72, 1, 2, 3, 76, 77, 6, 79, 16, 81, 2 (list; graph; refs; listen; history; internal format)
OFFSET

1,2

COMMENTS

a(n)<=n; a(a(n))=a(n).

All factors p^m of a(n) are of the form p=2 or p=4*k+3.

FORMULA

Multiplicative with a(p)=(if p==1 (mod 4) then 1 else p).

EXAMPLE

a(90)=a(2*3*3*5)=a(2*(4*0+3)^2*(4*1+1)^1=2*3^2*1=18.

CROSSREFS

Cf. A072436, A004144, A002144, A002145.

Sequence in context: A049073 A076388 A109680 * A132739 A060791 A116912

Adjacent sequences:  A072435 A072436 A072437 * A072439 A072440 A072441

KEYWORD

nonn,mult

AUTHOR

Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Jun 17 2002

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Last modified February 15 10:28 EST 2012. Contains 205763 sequences.