A300243 - OEIS

A300243

Filter sequence combining A051953(n) and A009195(n), n-phi(n) (cototient of n) and gcd(n,n-phi(n)).

1, 2, 2, 3, 2, 4, 2, 5, 6, 7, 2, 8, 2, 9, 10, 11, 2, 12, 2, 13, 14, 15, 2, 16, 17, 18, 19, 20, 2, 21, 2, 22, 23, 24, 25, 26, 2, 27, 28, 29, 2, 30, 2, 31, 32, 33, 2, 34, 35, 36, 37, 38, 2, 39, 40, 41, 32, 42, 2, 43, 2, 44, 45, 46, 47, 48, 2, 49, 50, 48, 2, 51, 2, 52, 53, 54, 47, 55, 2, 56, 57, 58, 2, 59, 60, 61, 62, 63, 2, 64, 37, 65, 66, 67, 68, 69, 2, 70, 71

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OFFSET

1,2

COMMENTS

Restricted growth sequence transform of P(A051953(n), A009195(n)), where P(a,b) is a two-argument form of A000027 used as a Cantor pairing function N x N -> N.

LINKS

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

EXAMPLE

a(66) = a(70) (= 48) because A051953(66) = A051953(70) = 46 and A009195(66) = A009195(70) = 2.

PROG

(PARI)

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; };

write_to_bfile(start_offset, vec, bfilename) = { for(n=1, length(vec), write(bfilename, (n+start_offset)-1, " ", vec[n])); }

A009195(n) = gcd(n, eulerphi(n));

A051953(n) = (n - eulerphi(n));

Aux300243(n) = (1/2)*(2 + ((A051953(n)+A009195(n))^2) - A051953(n) - 3*A009195(n));

write_to_bfile(1, rgs_transform(vector(65537, n, Aux300243(n))), "b300243.txt");

CROSSREFS

Cf. A009195, A051953.

Cf. also A300233, A300240, A300241, A300242.

Sequence in context: A369050 A300833 A373150 * A300241 A320014 A319693

Adjacent sequences: A300240 A300241 A300242 * A300244 A300245 A300246

KEYWORD

nonn

AUTHOR

Antti Karttunen, Mar 02 2018

STATUS

approved