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URL: https://oeis.org/A379006

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A379006
Ordinal transform of A355582, where A355582 is the largest 5-smooth divisor of n.
4
1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 3, 1, 4, 2, 1, 1, 5, 1, 6, 1, 2, 3, 7, 1, 1, 4, 1, 2, 8, 1, 9, 1, 3, 5, 2, 1, 10, 6, 4, 1, 11, 2, 12, 3, 1, 7, 13, 1, 14, 1, 5, 4, 15, 1, 3, 2, 6, 8, 16, 1, 17, 9, 2, 1, 4, 3, 18, 5, 7, 2, 19, 1, 20, 10, 1, 6, 21, 4, 22, 1, 1, 11, 23, 2, 5, 12, 8, 3, 24, 1, 25, 7, 9, 13, 6, 1, 26, 14, 3, 1, 27, 5, 28, 4, 2
OFFSET
1,7
LINKS
PROG
(PARI)
up_to = 20000;
ordinal_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), pt); for(i=1, length(invec), if(mapisdefined(om, invec[i]), pt = mapget(om, invec[i]), pt = 0); outvec[i] = (1+pt); mapput(om, invec[i], (1+pt))); outvec; };
is_A051037(n) = (n<7||vecmax(factor(n, 6)[, 1])<7); \\ From A051037
A355582(n) = fordiv(n, d, if(is_A051037(n/d), return(n/d)));
v379006 = ordinal_transform(vector(up_to, n, A355582(n)));
A379006(n) = v379006[n];
CROSSREFS
Cf. A355582.
Cf. A379005 (ordinal transform).
Cf. also A003602, A126760.
Sequence in context: A123541 A345062 A324537 * A090379 A254655 A344971
KEYWORD
nonn
AUTHOR
Antti Karttunen, Dec 15 2024
STATUS
approved