

A117477


Primes whose SOD and that of their indices are both prime and equal (indices may not be prime, but their SOD must be prime).


1



131, 263, 1039, 1091, 1301, 1361, 1433, 2221, 2441, 2591, 2663, 2719, 2803, 3433, 3631, 4153, 4357, 4397, 5507, 5701, 5741, 5927, 6311, 6353, 6553, 6737, 6827, 6971, 7013, 7213, 7411, 7523, 7741, 8821, 9103, 11173, 11353, 11731, 11821, 12277, 12347
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,1


COMMENTS

"SOD" = "sum of digits".
This sequence is a subset of A033548, the difference being that this sequence requires prime SODs.


LINKS

Table of n, a(n) for n=1..41.


FORMULA

Find primes whose indices, when SODs are computed, are both prime and SOD(i) = SOD(p)


EXAMPLE

a(3) = 1039, the 175th prime. Both the SOD of the index and the prime are prime and equal: 13 = 13.


PROG

UBASIC 20 'SOD prime index and SOD prime 30 Y=1 40 Y=nxtprm(Y) 50 C=C+1:print C; Y; ""; 60 D=str(C):Z=str(Y) 70 E=len(D):F=len(Z) 80 for Q=2 to E 90 A=mid(D, Q, 1):G=val(A) 100 I=I+G:print I; 110 next Q 120 for R=2 to F 130 B=mid(Z, R, 1):H=val(B) 140 J=J+H:print J; 150 next R 160 if I=prmdiv(I) and J=prmdiv(J) and I=J then stop 170 I=0:J=0 180 goto 40


CROSSREFS

Cf. A117478, A033548A033549, A117458A117463.
Sequence in context: A207527 A132249 A033548 * A089316 A242846 A142129
Adjacent sequences: A117474 A117475 A117476 * A117478 A117479 A117480


KEYWORD

easy,nonn,base


AUTHOR

Enoch Haga, Mar 19 2006


STATUS

approved



