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A261220 Ranks of involutions in permutation orderings A060117 and A060118.

%I A261220 #13 Aug 17 2016 22:16:55
%S A261220 0,1,2,4,6,7,12,16,18,20,24,25,26,28,48,49,60,66,72,76,78,90,96,98,
%T A261220 102,108,120,121,122,124,126,127,132,136,138,140,240,241,242,244,288,
%U A261220 289,312,316,336,338,360,361,372,378,384,385,432,450,456,468,480,484,486,498,504,508,528,546,576,582,600,602,606,612,624,626,648,660,672,678,720,721
%N A261220 Ranks of involutions in permutation orderings A060117 and A060118.
%C A261220 From _Antti Karttunen_, Aug 17 2016: (Start)
%C A261220 Intersection of A275804 and A276005. In other words, these are numbers in whose factorial base representation (A007623, see A260743) there does not exist any such pair of nonzero digits d_i and d_j in positions i and j that either (i - d_i) = j or (i - d_i) = (j - d_j) would hold. Here one-based indexing is used so that the least significant digit at right is in position 1.
%C A261220 (End)
%H A261220 Antti Karttunen, <a href="/A261220/b261220.txt">Table of n, a(n) for n = 0..1000</a>
%H A261220 <a href="/index/Fa#facbase">Index entries for sequences related to factorial base representation</a>
%o A261220 (Scheme, three variants, all requiring _Antti Karttunen_'s IntSeq-library)
%o A261220 (define A261220 (ZERO-POS 0 0 (lambda (n) (+ (A275947 n) (A276007 n)))))
%o A261220 (define A261220 (MATCHING-POS 0 0 (lambda (n) (>= 2 (A275803 n)))))
%o A261220 (define A261220 (MATCHING-POS 0 0 (lambda (n) (>= 2 (A060131 n)))))
%Y A261220 Intersection of A275804 and A276005.
%Y A261220 Same sequence shown in factorial base: A260743.
%Y A261220 Cf. A060117, A060118, A275947, A276007.
%Y A261220 Positions of zeros in A261219.
%Y A261220 Positions of 1 and 2's in A060131 and A275803.
%Y A261220 Subsequence: A060112.
%Y A261220 Cf. also A014489.
%K A261220 nonn,base
%O A261220 0,3
%A A261220 _Antti Karttunen_, Aug 26 2015