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%I #19 Jul 13 2016 12:02:55
%S 1,2,3,4,5,6,7,10,9,8,11,12,13,16,15,14,17,18,19,22,21,20,23,28,27,26,
%T 25,24,29,30,31,36,35,34,33,32,37,40,39,38,41,42,43,46,45,44,47,52,51,
%U 50,49,48,53,58,57,56,55,54,59,60,61,66,65,64,63,62,67,70,69,68,71,72
%N A permutation of the positive integers formed by reversing the order of the composites within each run of composites (1 and primes are left alone).
%H Alois P. Heinz, <a href="/A119257/b119257.txt">Table of n, a(n) for n = 1..20000</a>
%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%F a(n) = Sum_{k=1..2n} floor(cos^2(Pi*(n-1)!^(k-1)/(k-1)!)) - Sum_{k=1..n} floor(cos^2(Pi*(k-1)!^n/n!)). - _Anthony Browne_, May 24 2016
%e The run of composites (24,25,26,27,28) becomes (28,27,26,25,24).
%t Block[{$MaxExtraPrecision = 1000}, Table[Sum[Floor[Cos[Pi (n - 1)!^(k - 1)/(k - 1)!]^2], {k, 2 n}] - Sum[ Floor[Cos[Pi (k - 1)!^n/n!]^2], {k, n}], {n, 72}]] (* _Michael De Vlieger_, May 24 2016 *)
%o (PARI) {m=73; print1(1,","); n=2; while(n<=m, while(isprime(n), print1(n,","); n++); k=n; while(!isprime(n),n++); forstep(a=n-1,k,-1, print1(a,",")))} \\ _Klaus Brockhaus_, Aug 16 2006
%K nonn
%O 1,2
%A _Leroy Quet_, Jul 23 2006
%E More terms from _Klaus Brockhaus_, Aug 16 2006