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

Offset: 1

Author

Antti Karttunen, Feb 09 2024

Keywords

• nonn

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

Crossrefs

Setwise difference A369002 \ A369976.

Cf. A083345, A369001, A369974, A369975.

Programs

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(dA369001(n/d)*A369974(d),0)); mapput(memoA369974,n,v); (v)));
A369975(n) = (A369974(n)%2);
isA369977(n) = (A369001(n) && !A369975(n));