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A061394 Number of distinct prime factors of n-th least prime signature (A025487); also a(n)-th prime is largest prime factor of n-th least prime signature; also a(n)-th primorial number is largest primorial factor of n-th least product of primorial numbers. 9
0, 1, 1, 2, 1, 2, 1, 2, 3, 1, 2, 2, 3, 1, 2, 2, 3, 1, 2, 3, 2, 4, 2, 3, 1, 2, 3, 2, 4, 2, 3, 1, 2, 3, 2, 4, 2, 3, 3, 1, 3, 2, 4, 2, 3, 2, 4, 2, 3, 3, 1, 3, 2, 5, 4, 2, 3, 2, 4, 2, 3, 3, 1, 3, 2, 5, 4, 2, 3, 3, 2, 4, 3, 4, 2, 3, 4, 3, 2, 1, 3, 2, 5, 4, 2, 3, 3, 2, 4, 3, 4, 2, 5, 3, 4, 3, 2, 1, 3, 2, 5, 4, 2, 3, 3 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

A002110(a(n)) = A247451(n). - Reinhard Zumkeller, Sep 17 2014

Number of parts of the associated prime signature. - Álvar Ibeas, Nov 01 2014

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

a(n) = A061395(A025487(n)) = A001221(A025487(n)) = A051903(A181822(n)).

A000040(a(n)) = A006530(A025487(n)).

PROG

(Haskell)

import Data.List (elemIndex); import Data.Maybe (fromJust)

a061394 = fromJust . (`elemIndex` a002110_list) . a247451

-- Reinhard Zumkeller, Sep 17 2014

(PARI) isA025487(n)=my(k=valuation(n, 2), t); n>>=k; forprime(p=3, default(primelimit), t=valuation(n, p); if(t>k, return(0), k=t); if(k, n/=p^k, return(n==1)))

[omega(n) | n <- [1..1000], isA025487(n)]

\\ Or, for older versions:

apply(omega, select(isA025487, [1..1000])) \\ Charles R Greathouse IV, Nov 07 2014

CROSSREFS

Cf. A002110, A247451, A006530, A061395, A025487, A000040, A051903. A001221 by prime signature.

Sequence in context: A136109 A105265 A193360 * A248141 A220694 A136314

Adjacent sequences:  A061391 A061392 A061393 * A061395 A061396 A061397

KEYWORD

nonn

AUTHOR

Henry Bottomley, Apr 30 2001

EXTENSIONS

Offset updated by Matthew Vandermast, Nov 08 2008

STATUS

approved

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Last modified September 23 23:21 EDT 2018. Contains 315306 sequences. (Running on oeis4.)