1,1

The range of the sequence is generated by the context-sensitive grammar with decimal digits as terminals, {s,x,y,z,c,u,v,L,R} as non-terminals, s as axiom and the following rules (e is the empty word): s->L1xy1R, L->e, R->e, xy->e, 0x->1u, 1x->x0, Lx->L1u, u1->1u, u0->0u, uy->uz, zi->iz for 0<=i<=9, ziR->vjR for j=i+1 and 0<=i<9, z9R->c0R, ic->vj for j=i+1 and 0<=i<9, 9c->c0, iv->vi for 0<=i<=9, uv->xy and uc->xy1.

Michael S. Branicky, Table of n, a(n) for n = 1..10000

a:= n-> parse(cat(convert(n, binary), n)):

seq(a(n), n=1..35); # Alois P. Heinz, Jul 31 2022

Table[FromDigits[Join[IntegerDigits[n, 2], IntegerDigits[n]]], {n, 30}] (* Harvey P. Dale, Dec 13 2011 *)

(Python)

def a(n): return int(bin(n)[2:]+str(n))

print([a(n) for n in range(1, 34)]) # Michael S. Branicky, Jul 31 2022

(PARI) a(n) = fromdigits(binary(n))*10^(logint(n, 10)+1) + n; \\ Kevin Ryde, Nov 10 2022

Cf. A000027, A007088.

Sequence in context: A180280 A100580 A253631 * A054421 A037700 A037609

Adjacent sequences: A087741 A087742 A087743 * A087745 A087746 A087747

nonn,base,easy

Reinhard Zumkeller, Oct 02 2003

a(30) and beyond from Michael S. Branicky, Jul 31 2022

approved