A119711 - OEIS

%I #10 Sep 24 2019 07:08:59

%S 229,241,373,1831,2053,2503,3109,5861,6053,6151,6871,8293,8821,9161,

%T 9829,12049,13591,13781,14293,14887,16087,17737,19141,19333,20389,

%U 21493,23333,23509,24151,25771,27109,28807,29269,31337,33413,33941,35509

%N Primes p such that p+1, p+2 and p+3 have equal number of divisors.

%H Amiram Eldar, <a href="/A119711/b119711.txt">Table of n, a(n) for n = 1..10000</a>

%e 229 is OK since 230, 231 and 232 all have 8 divisors: {1,2,5,10,23,46,115,230}, {1,3,7,11,21,33,77,231} and {1,2,4,8,29,58,116,232}.

%t Select[Prime@Range@5000,DivisorSigma[0,#+1]==DivisorSigma[0,#+2]==DivisorSigma[0,#+3]&]

%Y Cf. A008329, A049234.

%K nonn

%O 1,1

%A _Zak Seidov_, Jul 29 2006