A119711 Primes p such that p+1, p+2 and p+3 have equal number of divisors.
229, 241, 373, 1831, 2053, 2503, 3109, 5861, 6053, 6151, 6871, 8293, 8821, 9161, 9829, 12049, 13591, 13781, 14293, 14887, 16087, 17737, 19141, 19333, 20389, 21493, 23333, 23509, 24151, 25771, 27109, 28807, 29269, 31337, 33413, 33941, 35509
Offset: 1
Keywords
Examples
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}.
Links
- Amiram Eldar, Table of n, a(n) for n = 1..10000
Programs
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Mathematica
Select[Prime@Range@5000,DivisorSigma[0,#+1]==DivisorSigma[0,#+2]==DivisorSigma[0,#+3]&]