A259643 - OEIS

A259643

Numbers n such that sum of first n odd primes divides product of first n odd primes.

1, 3, 5, 11, 25, 29, 41, 49, 51, 59, 69, 81, 99, 103, 113, 131, 133, 135, 147, 149, 153, 181, 187, 193, 197, 199, 205, 211, 213, 217, 219, 229, 235, 239, 243, 255, 271, 277, 281, 287, 289, 303, 309, 313, 323, 333, 335, 343, 347, 357, 359, 365, 367, 381, 383, 389

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

Obviously, a(n) is always an odd number.

LINKS

Table of n, a(n) for n=1..56.

EXAMPLE

a(1) = 1 because prime(2) mod prime(2) = 3 mod 3 = 0.

a(2) = 3 because (prime(2) * prime(3) * prime(4)) mod (prime(2) + prime(3) + prime(4)) = 105 mod 15 = 0.

a(3) = 5 because (prime(2) * prime(3) * prime(4) * prime(5) * prime(6)) mod (prime(2) + prime(3) + prime(4) + prime(5) + prime(6)) = 15015 mod 39 = 0.

MATHEMATICA

Module[{nn=400, op}, op=Prime[Range[2, nn+1]]; Select[Range[nn], Divisible[ Times@@ Take[op, #], Total[Take[op, #]]]&]] (* Harvey P. Dale, Nov 16 2022 *)

PROG

for(n=1, 1e3, if( prod(k=1, n, prime(k+1)) % sum(k=1, n, prime(k+1)) == 0 , print1(n", ")))

CROSSREFS

Cf. A051838, A065091, A070826, A071089, A071148, A262807.

Sequence in context: A214873 A330951 A018116 * A167796 A261896 A285184

Adjacent sequences: A259640 A259641 A259642 * A259644 A259645 A259646

KEYWORD

nonn,easy

AUTHOR

Altug Alkan, Oct 02 2015

STATUS

approved