A153022 Numbers k such that 1 plus the sum of squares of the first k primes is divisible by k+1.

6, 10, 150, 238, 56824, 665460, 18468766, 193274008, 635705422, 790546908, 33256634229, 66874977806, 68066767730

Offset

1,1

Comments

No further term <200000. [R. J. Mathar, Jan 17 2009]

a(11) > pi(10^11). [Donovan Johnson, Mar 10 2010]

a(14) > 118*10^9. - Robert Price, Apr 10 2013

Links

Table of n, a(n) for n=1..13.

Formula

{n: n+1 | A024525(n) }. [R. J. Mathar, Jan 17 2009]

Example

1 plus the sum of squares of the first 6 primes: (1 + 2^2 + 3^2 + ... + 13^2)/7 = 54, thus 6 is an element of the sequence.

Mathematica

okQ[k_]:=Mod[Total[Prime[Range[k]]^2]+1, k+1]==0; Select[Range[10^3], okQ] (* James C. McMahon, Nov 26 2025 *)

Crossrefs

Cf. A111441, A045345, A140480

Sequence in context: A359332 A352132 A124902 * A262081 A268537 A115677

Adjacent sequences: A153019 A153020 A153021 * A153023 A153024 A153025

Keyword

nonn,more

Author

Ctibor O. Zizka, Dec 16 2008

Extensions

a(5) from R. J. Mathar, Jan 17 2009

a(6)-a(10) from Donovan Johnson, Mar 10 2010

a(11)-a(13) from Robert Price, Apr 10 2013

Status

approved