A292566 - OEIS

A292566

Primes that can be reached with their prime-index, if you start with the prime-index and use iterations of A062028.

2, 11, 107, 191, 587, 719, 1061, 1171, 1181, 1259, 1327, 1487, 1597, 1619, 1933, 1949, 2011, 2141, 2269, 2477, 2803, 2999, 3041, 3049, 3079, 3169, 3229, 3259, 3617, 3733, 4493, 4799, 5009, 5023, 5171, 5261, 5581, 5657, 6131, 6211, 6301, 6311, 6421, 6451, 6529

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OFFSET

1,1

COMMENTS

If p is in the sequence, its index A000720(p) is not divisible by 3. - Robert Israel, Sep 19 2017

LINKS

Table of n, a(n) for n=1..45.

EXAMPLE

The prime-index of 11 is 5: 5+5=10, 10+1+0=11 -> after two iterations you reach 11, so 11 is in the sequence.

MAPLE

f:= proc(n) local t, p;

p:= ithprime(n);

t:= n;

t:= t + convert(convert(t, base, 10), `+`);

if t > p then return NULL

elif t = p then return p

od;

end proc:

map(f, [$1..1000]); # Robert Israel, Sep 19 2017

MATHEMATICA

ok[p_] := Block[{n = PrimePi@ p}, While [n < p, n += Total@ IntegerDigits@ n]; n == p]; Select[Prime@ Range@ 600, ok] (* Giovanni Resta, Sep 19 2017 *)

PROG

(PARI) is(n) = my(x=primepi(n)); while(1, x=x+sumdigits(x); if(x==n, return(1), if(x > n, return(0))))

forprime(p=1, 7000, if(is(p), print1(p, ", "))) \\ Felix Fröhlich, Sep 19 2017

CROSSREFS

Cf. A000720, A062028, A007618, A004207.

Sequence in context: A118805 A198001 A207155 * A365106 A053988 A141314

Adjacent sequences: A292563 A292564 A292565 * A292567 A292568 A292569

KEYWORD

nonn,base

AUTHOR

Peter Weiss, Sep 19 2017

EXTENSIONS

More terms from Felix Fröhlich, Sep 19 2017

STATUS

approved