A267277 Zeroless primes p such that p*(product of digits of p)+(sum of digits of p) is also prime.

11, 13, 17, 19, 31, 37, 43, 47, 61, 73, 79, 83, 223, 227, 263, 281, 283, 463, 643, 683, 821, 827, 881, 1117, 1231, 1259, 1291, 1321, 1361, 1367, 1433, 1471, 1543, 1567, 1583, 1597, 1619, 1637, 1657, 1699, 1723, 1741, 1753, 1777, 1933, 1951, 1973

Offset

1,1

Comments

Zeroless means that the decimal expansion has no digit "0", so no element of A056709 is in the sequence.

If we define a function "n*times products of digits plus sum of digits", f(n) = n*A007954(n) + A007953(n), then iterating the function starting at 217421 generates a chain of at least 4 primes: 217421 -> 24351169 -> 157795575151 -> 1522234189034803183.

Links

Robert Israel, Table of n, a(n) for n = 1..10000

Example

19 => 19*1*9+1+9 = 181 (is prime).
821 => 821*8*2*1+8+2+1 = 13147 (is prime).
2357 => 2357*2*3*5*7+2+3+5+7 = 494987 (is prime).
99995999 => 99995999*(9^7)*5+9*7+5 = 2391388816705223 (is prime).

Maple

isA267277 := proc(n)
    local pdgs ;
    if isprime(n) then
        pdgs := A007954(n) ;
        if pdgs <> 0 then
            isprime(n*pdgs+A007953(n)) ;
        else
            false;
        end if;
    else
        false;
    end if;
end proc:
for n from 1 to 400 do
    if isA267277(n) then
        printf("%d, \n", n);
    end if;
end do: # R. J. Mathar, Jan 16 2016

Mathematica

Select[Prime@ Range@ 480, And[Last@ DigitCount@ # == 0, PrimeQ[Function[k, # Times @@ k + Total@ k]@ IntegerDigits@ #]] &] (* Michael De Vlieger, Jan 12 2016 *)

Crossrefs

Cf. A007953, A007954, A038618, A056709.

Sequence in context: A168446 A275467 A045798 * A155071 A003626 A154981

Adjacent sequences: A267274 A267275 A267276 * A267278 A267279 A267280

Keyword

nonn,base,less,easy

Author

Emre APARI, Jan 12 2016

Status

approved