A242646 -id:A242646 - cp's OEIS frontend

A242645 a(n) = concatenation of decimal expansions of powers of 11 (in decreasing order).

1, 111, 121111, 1331121111, 146411331121111, 161051146411331121111, 1771561161051146411331121111, 194871711771561161051146411331121111, 214358881194871711771561161051146411331121111, 2357947691214358881194871711771561161051146411331121111

Offset: 0

N. J. A. Sloane, May 23 2014

A068704(11) (presently unknown) is either 0, if every term here is composite, or the index of the first prime in the sequence.

Alois P. Heinz, Table of n, a(n) for n = 0..42

Cf. A068704, A242646.

a:= proc(n) option remember;
      `if`(n=0, 1, parse(cat(11^n, a(n-1))))
    end:
seq(a(n), n=0..10);  # Alois P. Heinz, May 24 2014

a(n) is the concatenation of 11^n, 11^(n-1), ..., 121, 11, 1.

A386552 Concatenate powers of 10.

Original entry on oeis.org

1, 110, 110100, 1101001000, 110100100010000, 110100100010000100000, 1101001000100001000001000000, 110100100010000100000100000010000000, 110100100010000100000100000010000000100000000, 1101001000100001000001000000100000001000000001000000000

Offset: 0

Jason Bard, Jul 25 2025

Binary version of A045507. Base-2 representation of A164894.

Concatenate first A000217(n+1) terms of A010054.

Jason Bard, Table of n, a(n) for n = 0..43

Cf. A000096, A000217, A010054, A011557, A045507, A051639, A101305, A133082, A164894, A242646.

a:= proc(n) option remember;
      `if`(n<0, 0, parse(cat(a(n-1), 10^n)))
    end:
seq(a(n), n=0..10);  # Alois P. Heinz, Jul 28 2025

a[0] = 1; a[n_] := a[n - 1]*10^(n+1) + 10^n; Table[a[n], {n, 0, 9}]

def A386552(n): return 10**n*sum(10**(k*((n<<1)-k+1)>>1) for k in range(n+1)) # Chai Wah Wu, Aug 05 2025

a(n) = Sum_{k=1..n+1} 10^A133082(k,n+2).
a(n) = A101305(n) + 10^A000096(n).
For n >= 1, a(n) = 10^(n+1)*a(n-1)+10^n.
Number of digits in a(n) is A000217(n+1).

cp's OEIS Frontend

A242645 a(n) = concatenation of decimal expansions of powers of 11 (in decreasing order).

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