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A261198 Start with n and repeat the map x -> x+sumdigits(x) until reaching a prime, which is a(n), or 0 if no prime is reached. 1
2, 23, 0, 23, 11, 0, 19, 23, 0, 11, 13, 0, 17, 19, 0, 23, 37, 0, 29, 41, 0, 41, 101, 0, 37, 41, 0, 101, 59, 0, 43, 37, 0, 41, 43, 0, 47, 101, 0, 59, 67, 0, 89, 59, 0, 67, 71, 0, 101, 89, 0, 59, 61, 0, 89, 67, 0, 71, 73, 0, 103, 101, 0, 127, 89, 0, 109, 103, 0, 101, 79, 0, 83, 127, 0, 89, 101, 0, 109, 109, 0, 103, 107, 0, 127, 101, 0, 109, 113, 0, 101, 103, 0, 107, 109, 0, 113, 127, 0, 101 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Multiples of 3 never reach a prime because (multiple(3) + sumdigits of (multiple(3)) is always a multiple of 3.

LINKS

Maghraoui Abdelkader, Table of n, a(n) for n = 1..100

EXAMPLE

a(3)=0; a(6)=0; a(9)=0  as 3,6,9 are multiples of 3.

n=2; a0=2; a1=2+sumdigits(2)=4; a2=4+sumdigits(4)=8; a3=8+sumdigits(8)=16;

a4=16+sumdigits(16)=16+7=23; a4 is prime, so a(2)=23;

a(14)=14+(1+4=19); 19 is prime.

a(16)=16+(1+6)=23; 23 is prime.

PROG

(PARI)

verif(n)={if((n%3)==0, print1(0, ", "); return(); );

b=1; a=n;

while(b<10, a=a+sumdigits(a) ; if(isprime(a), print1(a, ", "); b=20))}

for(n=1, 100, verif(n); )

CROSSREFS

Cf. A000040, A001651, A008585, A154561.

Sequence in context: A246852 A060601 A053952 * A052077 A124604 A329336

Adjacent sequences:  A261195 A261196 A261197 * A261199 A261200 A261201

KEYWORD

nonn,base

AUTHOR

Maghraoui Abdelkader, Sep 30 2015

STATUS

approved

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Last modified August 6 12:33 EDT 2020. Contains 336246 sequences. (Running on oeis4.)