A109431 Binary strings that have 1's where 'evil numbers' occur, 0's elsewhere and every term ends with the n-th evil number index (counting with 0 = first).

1, 1001, 100101, 1001011, 1001011001, 10010110011, 1001011001101, 1001011001101001, 100101100110100101, 1001011001101001011, 100101100110100101101, 100101100110100101101001, 1001011001101001011010011, 1001011001101001011010011001, 100101100110100101101001100101

Offset

1,2

Comments

a(431) is an anti-yarborough prime with 861 digits (certified). Are there any more?

Links

Andrew Howroyd, Table of n, a(n) for n = 1..200

Example

a(4)=1001011 because it has 1's at the 'evil number' indices 0, 3, 5 and 6.

Prog

(PARI) a(n)={my(k=0, r=0, L=List()); while(r<n, listput(L, hammingweight(k)%2==0); if(L[#L], r++); k++); fromdigits(Vec(L))} \\ Andrew Howroyd, Nov 08 2019

Crossrefs

Cf. A001969, A109432.

Sequence in context: A192776 A218640 A221347 * A267599 A140927 A261544

Adjacent sequences: A109428 A109429 A109430 * A109432 A109433 A109434

Keyword

base,easy,nonn

Author

Jason Earls, Jun 28 2005

Extensions

Terms a(13) and beyond from Andrew Howroyd, Nov 08 2019

Status

approved