A283560 Concatenation of the first n nonsquares (A000037).

2, 23, 235, 2356, 23567, 235678, 23567810, 2356781011, 235678101112, 23567810111213, 2356781011121314, 235678101112131415, 23567810111213141517, 2356781011121314151718, 235678101112131415171819, 23567810111213141517181920

Offset

1,1

Comments

There are 5 primes in the first 6100 terms of this sequence, see A283561.

Links

Robert Israel, Table of n, a(n) for n = 1..365

Eric Weisstein's World of Mathematics, Consecutive Number Sequences

Maple

A[1]:= 2:
x:= 2:
for n from 2 to 20 do
  if issqr(x+1) then x:= x+2 else x:= x+1 fi;
  A[n]:= A[n-1]*10^(1+ilog10(x))+x;
od:
seq(A[n], n=1..20); # Robert Israel, Mar 13 2017

Mathematica

cns[n_]:=FromDigits[Flatten[IntegerDigits[Table[k+Floor[1/2+Sqrt[k]], {k, 1, n}]]]]
Module[{nn=20, sqf}, sqf=Select[Range[2, nn], !IntegerQ[Sqrt[#]]&]; Table[FromDigits[Flatten[ IntegerDigits/@ Take[sqf, n]]], {n, Length[sqf]}]] (* Harvey P. Dale, Sep 07 2024 *)

Prog

(PARI) a(n)=my(s=""); for(k=1, n, s=Str(s, (sqrtint(4*k)+1)\2 + k)); eval(s) \\ Charles R Greathouse IV, Mar 10 2017

Crossrefs

Cf. A000037, A007908, A019521, A283561.

Sequence in context: A112782 A093672 A262571 * A159902 A301339 A294268

Adjacent sequences: A283557 A283558 A283559 * A283561 A283562 A283563

Keyword

base,nonn,changed

Author

XU Pingya, Mar 10 2017

Status

approved