A319339 - OEIS

A319339

Filter sequence combining A081373(n) with A246277(n).

1, 2, 3, 4, 3, 5, 3, 6, 4, 7, 3, 8, 3, 9, 10, 11, 3, 12, 3, 13, 14, 15, 3, 16, 17, 18, 6, 19, 3, 20, 3, 21, 22, 23, 10, 24, 3, 25, 15, 26, 3, 27, 3, 28, 29, 30, 3, 31, 4, 32, 33, 34, 3, 35, 14, 36, 37, 38, 3, 39, 3, 40, 13, 41, 42, 43, 3, 44, 45, 46, 3, 47, 3, 48, 49, 50, 51, 52, 3, 53, 54, 55, 3, 56, 57, 58, 59, 60, 3, 61, 14, 62, 63, 64, 18, 65, 3, 66, 19

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OFFSET

1,2

COMMENTS

Restricted growth sequence transform of ordered pair [A081373(n), A246277(n)].

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; };

rgs_transform(invec) = { my(om = Map(), outvec = vector(length(invec)), u=1); for(i=1, length(invec), if(mapisdefined(om, invec[i]), my(pp = mapget(om, invec[i])); outvec[i] = outvec[pp] , mapput(om, invec[i], i); outvec[i] = u; u++ )); outvec; };

v081373 = ordinal_transform(vector(up_to, n, eulerphi(n)));

A081373(n) = v081373[n];

A246277(n) = if(1==n, 0, my(f = factor(n), k = primepi(f[1, 1])-1); for (i=1, #f~, f[i, 1] = prime(primepi(f[i, 1])-k)); factorback(f)/2);

v319339 = rgs_transform(vector(up_to, n, [A081373(n), A246277(n)]));

A319339(n) = v319339[n];

CROSSREFS

Cf. A081373, A246277, A300247, A305801, A305897, A318500.

Sequence in context: A323238 A319701 A355833 * A322807 A322805 A322809

Adjacent sequences: A319336 A319337 A319338 * A319340 A319341 A319342

KEYWORD

nonn

AUTHOR

Antti Karttunen, Sep 24 2018

STATUS

approved