

A339867


Primes p such that p + sigma(p1) and p + sigma(p+1) are both prime.


1



13, 23, 41, 43, 53, 59, 61, 67, 131, 167, 193, 227, 263, 271, 283, 293, 311, 313, 397, 503, 523, 563, 571, 599, 607, 631, 653, 661, 701, 743, 827, 839, 907, 911, 919, 941, 947, 1031, 1087, 1103, 1171, 1181, 1187, 1301, 1319, 1321, 1381, 1499, 1531, 1559, 1619, 1621, 1663, 1741, 1747, 1811, 1847
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OFFSET

1,1


COMMENTS

Terms with sigma(p1) = sigma(p+1) include 919, 334541 and 463219.


LINKS



EXAMPLE

a(3) = 41 is a term because 41 is prime, 41 + sigma(40) = 41+1+2+4+5+8+10+20+40=131 is prime, and 41 + sigma(42) = 41+1+2+3+6+7+14+21+42=137 is prime.


MAPLE

select(t > isprime(t + numtheory:sigma(t1)) and isprime(t + numtheory:sigma(t+1)), [seq(ithprime(i), i=1..300)])


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



