A331178 - OEIS

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A331178

Number of values of k, 1 <= k <= n, with A023900(k) = A023900(n), where A023900 is Dirichlet inverse of Euler totient function phi.

1, 1, 1, 2, 1, 1, 1, 3, 2, 1, 1, 2, 1, 1, 1, 4, 1, 3, 1, 2, 1, 1, 1, 4, 2, 2, 3, 2, 1, 1, 1, 5, 1, 1, 1, 5, 1, 1, 2, 3, 1, 2, 1, 2, 2, 1, 1, 6, 2, 4, 1, 3, 1, 7, 1, 3, 1, 1, 1, 2, 1, 1, 4, 6, 1, 1, 1, 2, 1, 1, 1, 8, 1, 2, 3, 2, 1, 2, 1, 5, 4, 2, 1, 3, 1, 1, 1, 3, 1, 3, 1, 2, 2, 1, 2, 9, 1, 4, 2, 6, 1, 1, 1, 5, 1

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OFFSET

1,4

COMMENTS

Ordinal transform of A023900.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..65537

PROG

(PARI)

up_to = 65537;

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; };

A023900(n) = factorback(apply(p -> 1-p, factor(n)[, 1]));

v331178 = ordinal_transform(vector(up_to, n, A023900(n)));

A331178(n) = v331178[n];

CROSSREFS

Cf. A000010, A023900.

Cf. also A081373, A331175, A331179, A331180.

Sequence in context: A322885 A292582 A008479 * A227350 A107345 A358780

Adjacent sequences: A331175 A331176 A331177 * A331179 A331180 A331181

KEYWORD

nonn

AUTHOR

Antti Karttunen, Jan 11 2020

STATUS

approved