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A209280 First difference of A050289 = numbers whose digits are a permutation of (1,...,9). 7
9, 81, 18, 81, 9, 702, 9, 171, 27, 72, 18, 693, 18, 72, 27, 171, 9, 702, 9, 81, 18, 81, 9, 5913, 9, 81, 18, 81, 9, 1602, 9, 261, 36, 63, 27, 594, 18, 162, 36, 162, 18, 603, 9, 171, 27, 72, 18, 5814, 9, 171, 27, 72, 18, 603, 9, 261, 36, 63, 27, 1584, 27, 63, 36, 261, 9 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

This sequence is the natural extension of A107346 (and others, see below) from 5!-1 to 9!-1 terms, which is the natural (since maximal) length, given that OEIS sequence data is stored as decimal numbers. OTOH, it is quite different from A219664 in many aspects, not only for the reason that the other sequence is infinite and therefore differs from this one in all terms beyond n = 9!-1.

The sequence is finite, with 9!-1 terms, and symmetric: a(n)=a(9!-n).

All terms are a multiple of 9, cf. formula.

The subsequence of the first n!-1 terms (n=2,...9) yields the first differences of the sequence of numbers whose digits are a permutation of (1,...,n):

The first 8!-1 terms yield the first differences of A178478: numbers whose digits are a permutation of 12345678.

The first 7!-1 terms yield the first differences of A178477: numbers whose digits are a permutation of 1234567.

The first 6!-1 terms yield the first differences of A178476: numbers whose digits are a permutation of 123456.

The first 5!-1 terms yield A107346, the first differences of A178475: numbers whose digits are a permutation of 12345.

LINKS

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

FORMULA

a(n) = A219664(n) = 9*A217626(n) (for n < 9!). - M. F. Hasler, Jan 12 2013

a(n) = a(m!-n) for any m < 10 such that n < m!.

EXAMPLE

The same initial terms are obtained for the permutations of any set of the form {1,...,m}, e.g., {1,2,3} or {1,...,9}: In the first case we have P = (123,132,213,231,312,321) and P(4)-P(3) = 231-213 = 18 = a(3), and in the latter case P(4)-P(3)=123456897-123456879 = 18, again. - M. F. Hasler, Jan 12 2013

PROG

(PARI) A209280_list(N=5)={my(v=vector(N, i, 10^(N-i))~); v=vecsort(vector(N!, k, numtoperm(N, k)*v)); vecextract(v, "^1")-vecextract(v, "^-1")} \\ return the N!-1 first terms as a vector

(PARI) A209280(n)={if(a209280=='a209280 || #a209280<n, a209280=A209280_list(A090529(n+1))); a209280[n]}

CROSSREFS

Cf. A030299, A219664.

Sequence in context: A228591 A219664 A107346 * A014393 A008463 A203656

Adjacent sequences:  A209277 A209278 A209279 * A209281 A209282 A209283

KEYWORD

easy,nonn,base,fini

AUTHOR

M. F. Hasler, Jan 12 2013

STATUS

approved

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Last modified July 27 04:53 EDT 2017. Contains 289841 sequences.