A283561 Concatenation of the first a(n) nonsquares gives a prime.

1, 2, 5, 550, 832

Offset

1,2

Comments

Indices n for which A283560(n) is prime.

A283560(1) = 2, A283560(2) = 23, A283560(5) = 23567, A283560(550) = 23567810...570571572573 is 1554-digits prime, A283560(832) = 23567810...858859860861 is 2400-digits prime.

Next term, if there is, will be more than 6100.

Links

Table of n, a(n) for n=1..5.

Eric Weisstein's World of Mathematics, Consecutive Number Sequences

Mathematica

cns[n_]:=FromDigits[Flatten[IntegerDigits[Table[k+Floor[1/2+Sqrt[k]], {k, 1, n}]]]]
Select[Table[cns[n], {n, 6100}], PrimeQ]

Prog

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

Crossrefs

Cf. A000037, A019518, A046035, A283560.

Sequence in context: A163798 A081296 A133378 * A037063 A068105 A065588

Adjacent sequences: A283558 A283559 A283560 * A283562 A283563 A283564

Keyword

base,nonn,more

Author

XU Pingya, Mar 10 2017

Status

approved