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 A263458 Deal a pack of n cards into two piles and gather them up, n/2 times. All n such that this reverses the order of the deck. 0
 4, 6, 12, 22, 28, 30, 36, 46, 52, 60, 70, 78, 100, 102, 108, 126, 148, 150, 156, 166, 172, 180, 190, 196, 198, 222, 228, 238, 262, 268, 270, 276, 292, 310, 316, 348, 358, 366, 372, 382, 388, 396, 420, 430, 438, 460, 462, 478, 486, 502, 508, 540, 556, 598 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS This seems to be A003628(n)-1; that is, each element of this sequence is one less than a prime congruent to 5 or 7 modulo 8. LINKS Table of n, a(n) for n=1..54. EXAMPLE Take a deck of 52 playing cards. Deal it into two piles, then pick up the first pile and put it on top of the other. Do this 26 times. The order of the deck is reversed, so 52 belongs to this sequence. PROG (Sage) from itertools import cycle def into_piles(r, deck): packs = [[] for i in range(r)] for card, pack in zip(range(1, deck+1), cycle(range(r))): packs[pack].insert(0, card) out = sum(packs, []) return Permutation(out) def has_reversing_property(deck): p = power(into_piles(2, deck), deck/2) return p==into_piles(1, deck) [i for i in range(2, 400, 2) if has_reversing_property(i)] CROSSREFS Sequence in context: A027150 A020141 A049478 * A163776 A050558 A331192 Adjacent sequences: A263455 A263456 A263457 * A263459 A263460 A263461 KEYWORD nonn AUTHOR Christian Perfect, Oct 19 2015 STATUS approved

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Last modified May 29 03:17 EDT 2024. Contains 372921 sequences. (Running on oeis4.)