A207973 - OEIS

A207973

Primes p such that the equation prime(p-k)+k! = prime(p) has at least one solution k>0.

2, 31, 43, 67, 107, 151, 167, 179, 227, 233, 389, 509, 547, 661, 719, 769, 823, 829, 967, 1033, 1093, 1259, 1321, 1493, 1567, 1733, 1873, 2099, 2341, 2539, 2621, 2683, 2819, 2927, 3119, 3169, 3373

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OFFSET

1,1

COMMENTS

Apart from the first entry, the majority of the entries stem from k=4, i.e., this is essentially a reverse lookup within A033560. - R. J. Mathar, Mar 15 2012

LINKS

Table of n, a(n) for n=1..37.

EXAMPLE

2 is in the sequence because prime(2) = prime(2-1)+1 = 3,

31 is in the sequence because prime(31) = prime(31-4)+1*2*3*4 = 103+24 = 127,

43 is in the sequence because prime(43) = prime(43-4)+1*2*3*4 = 167+24 = 191.

PROG

(PARI) is_A207973(n)={local(k); k=1; while((k<n)&&(prime(n-k)+k!)<prime(n), k=k+1); if((k<n)&&(prime(n-k)+k!)==prime(n), isprime(n), 0)} \\ Michael B. Porter, Mar 22 2012

CROSSREFS

Cf. A000040, A000142.

Sequence in context: A215031 A120638 A101017 * A193423 A241484 A235477

Adjacent sequences: A207970 A207971 A207972 * A207974 A207975 A207976

KEYWORD

nonn

AUTHOR

Gerasimov Sergey, Mar 02 2012

STATUS

approved