A326442 Emirp-indexed emirps: emirps with emirp subscripts.

157, 991, 1217, 7057, 7523, 7649, 7841, 9293, 9661, 9833, 9923, 10009, 10079, 10457, 10487, 11447, 11927, 12301, 12547, 12763, 13469, 13513, 13693, 14177, 15511, 15683, 30557, 31033, 31069, 31267, 31277, 32299, 32341, 32911, 33029, 35363, 35801, 72559, 73453

Offset

1,1

Comments

Here the 'subscript' of an emirp is the index of it over all the primes, not over the emirps (otherwise we would get {A006567(A006567(n))} sorted). - Jianing Song, Oct 29 2019

Links

Metin Sariyar, Table of n, a(n) for n = 1..10000

Chris K. Caldwell and G. L. Honaker, Jr., Prime curio for 157

Example

157 is a term because 157, 751, pi(157) = 37 and 73 are all primes.

Mathematica

Do[y=IntegerReverse; z=PrimeQ; k=PrimePi[n]; a=y[n]; b=y[k]; If[!a==n&&!b==k&&z[a]&&z[b]&&z[n]&&z[k], Print[n]], {n, 1, 10^5}]

Prog

(PARI) is_emirps(n) = my(r=eval(concat(Vecrev(Str(n))))); isprime(r)&&r!=n&&isprime(n); \\ A006567
isok(n) = is_emirps(n) && is_emirps(primepi(n)); \\ Michel Marcus, Oct 14 2019

Crossrefs

Cf. A006450, A006567.

Sequence in context: A226972 A337427 A142766 * A258436 A167992 A038493

Adjacent sequences: A326439 A326440 A326441 * A326443 A326444 A326445

Keyword

nonn,base

Author

Metin Sariyar, Oct 09 2019

Status

approved