A224827 Primes p such that prime(floor(p/10) + (p mod 10)) = p.

64279, 64319, 64483, 64513, 64621

Offset

1,1

Comments

Subset of A224843. Sequence is clearly finite, since the ratio prime(n)/n is unbounded. By comparing prime(x/10) with x and using suitable functions which provide upper and lower bounds for prime(x), it is also possible to infer that no more terms exist. - Giovanni Resta, Jul 22 2013

Links

Table of n, a(n) for n=1..5.

Chris K. Caldwell and G. L. Honaker, Jr., Prime Curios! 64621

Example

prime(6462+1) = 64621 which is prime. Hence, 64621 is in sequence.

Maple

with(numtheory):KD := proc(p)
    ithprime((p-(p mod 10))/10 + (p mod 10))=p ;
end proc:
for p from 1 to 65000 do
    if KD(p) then
        printf("%d, ", p) ;
    end if;
end do:# K. D. Bajpai, Jul 21 2013
with(numtheory):K:=proc()local n, a, c, p; p:=3; c:=1; for n from 1 to 50000 do; p:=ithprime(n); a:= ithprime((p-(p mod 10))/10 + (p mod 10)); if  p=a  then lprint(c, p); c:=c+1; fi; od; end: K(); # K. D. Bajpai, Jul 21 2013

Prog

(PARI) is(p)=p==prime(p\10+p%10)&&isprime(p) \\ Charles R Greathouse IV, Jul 22 2013

Crossrefs

Cf. A224843.

Sequence in context: A031859 A182811 A236702 * A234128 A205631 A205333

Adjacent sequences: A224824 A224825 A224826 * A224828 A224829 A224830

Keyword

nonn,base,fini,full

Author

K. D. Bajpai, Jul 21 2013

Status

approved