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A355710
Numbers k such that k and k+1 have the same number of 5-smooth divisors.
4
2, 21, 33, 34, 38, 57, 85, 86, 93, 94, 104, 116, 122, 141, 145, 146, 154, 158, 171, 177, 182, 189, 201, 205, 213, 214, 218, 237, 265, 266, 273, 296, 302, 321, 326, 332, 334, 338, 344, 357, 362, 381, 385, 387, 393, 394, 398, 417, 445, 446, 453, 454, 475, 476, 482
OFFSET
1,1
COMMENTS
Numbers k such that A355583(k) = A355583(k+1).
LINKS
EXAMPLE
2 is a term since A355583(2) = A355583(3) = 2.
MATHEMATICA
s[n_] := Times @@ (1 + IntegerExponent[n, {2, 3, 5}]); Select[Range[500], s[#] == s[#+1] &]
PROG
(PARI) s(n) = (valuation(n, 2) + 1) * (valuation(n, 3) + 1) * (valuation(n, 5) + 1);
s1 = s(1); for(k = 2, 500, s2 = s(k); if(s1 == s2, print1(k-1, ", ")); s1 = s2);
CROSSREFS
Cf. A355583, A355709 (3-smooth analog).
Subsequences: A355711, A355712.
Sequence in context: A071761 A101316 A006920 * A089558 A266873 A215753
KEYWORD
nonn
AUTHOR
Amiram Eldar, Jul 15 2022
STATUS
approved