A369977 - OEIS

A369977

Numbers that are found in A369002, but not in its subsequence A369976.

81, 144, 225, 256, 400, 441, 625, 729, 784, 972, 1089, 1215, 1225, 1521, 1620, 1701, 1728, 1936, 2160, 2268, 2401, 2601, 2673, 2700, 2704, 2835, 2880, 3024, 3025, 3072, 3159, 3249, 3375, 3564, 3600, 3840, 4032, 4096, 4131, 4212, 4225, 4455, 4500, 4617, 4624, 4725, 4752, 4761, 4800, 5040, 5120, 5265, 5292, 5376

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

a(10) = 972 = 2^2 * 3^5 is the first term that is not a square.

LINKS

Antti Karttunen, Table of n, a(n) for n = 1..20000

PROG

(PARI)

A083345(n) = { my(f=factor(n)); numerator(vecsum(vector(#f~, i, f[i, 2]/f[i, 1]))); };

A369001(n) = !(A083345(n)%2);

memoA369974 = Map();

A369974(n) = if(1==n, 1, my(v); if(mapisdefined(memoA369974, n, &v), v, v = -sumdiv(n, d, if(d<n, A369001(n/d)*A369974(d), 0)); mapput(memoA369974, n, v); (v)));

A369975(n) = (A369974(n)%2);

isA369977(n) = (A369001(n) && !A369975(n));

CROSSREFS

Setwise difference A369002 \ A369976.

Cf. A083345, A369001, A369974, A369975.

Sequence in context: A046317 A046374 A153259 * A207050 A206072 A207043

Adjacent sequences: A369974 A369975 A369976 * A369978 A369979 A369980

KEYWORD

nonn

AUTHOR

Antti Karttunen, Feb 09 2024

STATUS

approved