

A068435


Consecutive prime powers without a prime between them.


0




OFFSET

1,1


COMMENTS

Only 5 pairs are known to 10^14.


LINKS

Table of n, a(n) for n=1..10.


EXAMPLE

8=2^3, 9=2^3, there is no prime between 8 and 9.
25=5^2, 27=3^3, there is no prime between 25 and 27.


PROG

(PARI) ispp(x) = !isprime(x) && isprimepower(x);
lista(nn=50000) = {my(prec = 0); for (i=1, nn, if (ispp(i), if (! prec, prec = i, if (primepi(i) == primepi(prec), print1(prec, ", ", i, ", ")); prec = i; ); ); ); } \\ Michel Marcus, Aug 24 2019


CROSSREFS

Cf. A025475, A060846, A067871, A246547.
Sequence in context: A077599 A109097 A115645 * A302554 A124438 A124184
Adjacent sequences: A068432 A068433 A068434 * A068436 A068437 A068438


KEYWORD

nonn,more,changed


AUTHOR

Jon Perry, Mar 09 2002


STATUS

approved



