

A060848


Difference between a nontrivial prime power (A025475) and the next prime.


1



1, 3, 2, 1, 4, 2, 5, 4, 3, 2, 6, 2, 3, 4, 8, 1, 4, 4, 6, 9, 12, 6, 4, 12, 6, 7, 30, 4, 12, 12, 5, 16, 6, 4, 10, 10, 12, 10, 6, 3, 4, 6, 10, 4, 6, 2, 4, 10, 6, 17, 4, 10, 4, 18, 6, 30, 12, 12, 4, 10, 27, 4, 6, 4, 12, 4, 28, 6, 2, 10, 4, 4, 10, 12, 18, 10, 10, 3, 12, 4, 12, 6, 10, 10, 18, 10, 12
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OFFSET

1,2


COMMENTS

a(n)=1 only for some powers of 2 corresponding to Fermat primes > 3.  Edited by Robert Israel, Jun 03 2021


LINKS



FORMULA



EXAMPLE

78125=5^7 is followed by 78137, the difference is 12.


MAPLE

N:= 10^5: # for prime powers <= N
S:= {}:
p:= 1:
do
p:= nextprime(p);
if p^2 > N then break fi;
S:= S union {seq(p^i, i=2..floor(log[p](N)))}
od:
map(t > nextprime(t)t, sort(convert(S, list))); # Robert Israel, Jun 03 2021


MATHEMATICA

NextPrime[#]#&/@Select[Range[100000], PrimePowerQ[#]&&!PrimeQ[#]&] (* Harvey P. Dale, Oct 19 2022 *)


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



