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%I #18 Sep 09 2017 19:31:03
%S 1,2,3,4,5,6,7,8,9,11,12,13,16,17,18,19,21,23,24,25,27,29,30,31,32,36,
%T 37,41,43,47,48,49,53,54,59,61,63,64,65,67,70,71,72,73,79,81,83,89,96,
%U 97,101,103,107,108,109,113,121,125,127,128,131,133,137,139,144
%N Fixed points of A242420.
%C A number n is present if its prime factorization n = p_a * p_b * p_c * ... * p_i * p_j * p_k^e_k, where a <= b <= c <= ... <= i <= j < k are the indices of prime factors, not necessarily all distinct, except that j < k, and the greatest prime divisor p_k [with k = A061395(n)] may occur multiple times, satisfies the condition that the first differences of those prime indices (a-0, b-a, c-b, ..., j-i, k-j) form a palindrome.
%H Antti Karttunen, <a href="/A243068/b243068.txt">Table of n, a(n) for n = 1..2185</a>
%e 4 = p_1^2 is present, as the first differences (deltas) of the prime indices (excluding the extra copies of the largest prime factor 2), form a palindrome: (1-0) = (1).
%e 18 = 2*3*3 = p_1 * p_2 * p_2 is present, as the deltas of the indices of its nondistinct prime factors, (excluding the extra copies of the largest prime factor 3) form a palindrome: (1-0, 2-1) = (1,1).
%e 60 = 2*2*3*5 = p_1 * p_1 * p_2 * p_3 is NOT present, as the deltas of prime indices (1-0, 1-1, 2-1, 3-2) = (1,0,1,1) do NOT form a palindrome.
%e Also, any of the cases mentioned in the Example section of A243058 as being present there, are also present in this sequence.
%o (Scheme, with _Antti Karttunen_'s IntSeq-library)
%o (define A243068 (FIXED-POINTS 1 1 A242420))
%Y Fixed points of A242420.
%Y Differs from A242413 for the first time at n=36, where a(36)=61, while A242413(36)=60.
%Y A000040 and A243058 are subsequences.
%Y Cf. A242414, A242417.
%K nonn
%O 1,2
%A _Antti Karttunen_, Jun 01 2014
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