A305890 Filter sequence for all such sequences b, for which b(A176997(k)) = constant for all k > 1, where A176997 is the union of odd primes and Fermat pseudoprimes.

1, 2, 3, 4, 3, 5, 3, 6, 7, 8, 3, 9, 3, 10, 11, 12, 3, 13, 3, 14, 15, 16, 3, 17, 18, 19, 20, 21, 3, 22, 3, 23, 24, 25, 26, 27, 3, 28, 29, 30, 3, 31, 3, 32, 33, 34, 3, 35, 36, 37, 38, 39, 3, 40, 41, 42, 43, 44, 3, 45, 3, 46, 47, 48, 49, 50, 3, 51, 52, 53, 3, 54, 3, 55, 56, 57, 58, 59, 3, 60, 61, 62, 3, 63, 64, 65, 66, 67, 3, 68, 69, 70, 71, 72, 73, 74, 3

Offset: 1

Author

Antti Karttunen, Jul 01 2018

Keywords

• nonn

Links

• Antti Karttunen, Table of n, a(n) for n = 1..101101

Crossrefs

Cf. A001567, A062173, A176997, A257531.

Differs from A305801 for the first time at n=341, where a(341) = 3, while A305801(341) = 275.

Programs

PARI

up_to = 100000;
A257531(n) = if(n==1, 0, if(Mod(2, n)^(n-1)==1, 1, 0));
partialsums(f,up_to) = { my(v = vector(up_to), s=0); for(i=1,up_to,s += f(i); v[i] = s); (v); }
vpartsums = partialsums(A257531, up_to);
Apartsums(n) = vpartsums[n];
A305890(n) = if(n<=2,n,if(A257531(n),3,1+n-Apartsums(n)));

Formula

For all i, j: A305801(i) = A305801(j) => a(i) = a(j) => A062173(i) = A062173(j).