A305904 Filter sequence for all such sequences S, for which S(A091206(k)) = constant for all k >= 3, where A091206 gives primes whose binary representation encodes a polynomial irreducible over GF(2).

1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 7, 11, 7, 12, 13, 14, 15, 16, 7, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 7, 28, 29, 30, 31, 32, 7, 33, 34, 35, 7, 36, 37, 38, 39, 40, 7, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 7, 52, 7, 53, 54, 55, 56, 57, 7, 58, 59, 60, 61, 62, 7, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 7

Offset: 1

Author

Antti Karttunen, Jun 16 2018

Keywords

• nonn

Comments

Restricted growth sequence transform of the ordered pair [A305900(n), A305903(n)].

For all i, j: a(i) = a(j) => A305815(i) = A305815(j).

Links

• Antti Karttunen, Table of n, a(n) for n = 1..100000
• Index entries for sequences operating on GF(2)[X]-polynomials

Crossrefs

Cf. A091206, A305815, A305816, A305817, A305900, A305903.

Programs

PARI

up_to = 100000;
A305816(n) = (isprime(n)&&polisirreducible(Pol(binary(n))*Mod(1,2)));
partialsums(f,up_to) = { my(v = vector(up_to), s=0); for(i=1,up_to,s += f(i); v[i] = s); (v); }
v305817 = partialsums(A305816, up_to);
A305817(n) = v305817[n];
A305904(n) = if(n<7,n,if(A305816(n),7,3+n-A305817(n)));

Formula

For n < 7, a(n) = n; for >= 7, a(n) = 7 if A305816(n) = 1 [when n is in A091206[3..] = 7, 11, 13, 19, 31, 37, 41, ...], and 3+n-A305817(n) otherwise.