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 A353807 Numbers k such that A353802(k) / sigma(sigma(k)) is an integer > 1, where A353802(n) = Product_{p^e||n} sigma(sigma(p^e)). 3
 1819, 5088, 7215, 7276, 9487, 9523, 11895, 13303, 14235, 16371, 20179, 21079, 21255, 24531, 24751, 24931, 25824, 29104, 30615, 32224, 33855, 36199, 37635, 37948, 38092, 38664, 40443, 40515, 41847, 43831, 44655, 45475, 45695, 45883, 46995, 48043, 48399, 53835, 54015, 54568, 55747, 56899, 56928, 59599, 60495, 61035 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Numbers k such that A353805(k) = 1, but A353806(k) > 1. LINKS EXAMPLE A353802(1819) = 10920 = 2*A051027(1819) = 2*5460, therefore 1819 is included as a term. PROG (PARI) A051027(n) = sigma(sigma(n)); A353805(n) = { my(f = factor(n)); (A051027(n) / gcd(A051027(n), prod(k=1, #f~, A051027(f[k, 1]^f[k, 2])))); }; A353806(n) = { my(f = factor(n), u=prod(k=1, #f~, A051027(f[k, 1]^f[k, 2]))); (u / gcd(A051027(n), u)); }; isA353807(n) = ((1==A353805(n)) && (1!=A353806(n))); CROSSREFS Cf. A000203, A051027, A353802, A353805, A353806. Cf. also A336561. Sequence in context: A205258 A255732 A338166 * A326236 A156636 A234660 Adjacent sequences: A353804 A353805 A353806 * A353808 A353809 A353810 KEYWORD nonn AUTHOR Antti Karttunen, May 08 2022 STATUS approved

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Last modified January 28 14:40 EST 2023. Contains 359895 sequences. (Running on oeis4.)