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A181815 a(n) = largest integer such that, when any of its divisors divides A025487(n), the quotient is a member of A025487. 6
1, 2, 4, 3, 8, 6, 16, 12, 5, 32, 9, 24, 10, 64, 18, 48, 20, 128, 36, 15, 96, 7, 27, 40, 256, 72, 30, 192, 14, 54, 80, 512, 144, 60, 384, 28, 108, 25, 160, 1024, 45, 288, 21, 81, 120, 768, 56, 216, 50, 320, 2048, 90, 576, 11, 42, 162, 240, 1536, 112, 432, 100, 640, 4096, 180, 1152 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

A permutation of the natural numbers.

The number of divisors of a(n) equals the number of ordered factorizations of A025487(n) as A025487(j)*A025487(k). Cf. A182762.

LINKS

Table of n, a(n) for n=1..65.

FORMULA

If A025487(n) is considered in its form as Product A002110(i)^e(i), then a(n) = Product p(i)^e(i). If A025487(n) is instead considered as Product p(i)^e(i), then a(n) = Product (p(i)/A008578(i))^e(i).

a(n) = A122111(A181820(n)). - Matthew Vandermast, May 21 2012

EXAMPLE

For any divisor d of 9 (d = 1, 3, 9), 36/d (36, 12, 4) is a member of A025487. 9 is the largest number with this relationship to 36; therefore, since 36 = A025487(11), a(11) = 9.

CROSSREFS

If this sequence is considered the "primorial deflation" of A025487(n) (see first formula), the primorial inflation of n is A108951(n), and the primorial inflation of A025487(n) is A181817(n).

A181820(n) is another mapping from the members of A025487 to the positive integers.

Sequence in context: A244981 A284571 A124833 * A168521 A244982 A101468

Adjacent sequences:  A181812 A181813 A181814 * A181816 A181817 A181818

KEYWORD

nonn

AUTHOR

Matthew Vandermast, Nov 30 2010

STATUS

approved

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Last modified January 22 09:52 EST 2019. Contains 319363 sequences. (Running on oeis4.)