|
|
A117458
|
|
Primes and their indices such that when their respective SOD's are both prime, the SOD of the index is the nextprime of the prime SOD.
|
|
5
|
|
|
227, 313, 1723, 2003, 2311, 2609, 3329, 3701, 4007, 4027, 4801, 4931, 5107, 7253, 10457, 12143, 12163, 12211, 12433, 12547, 13063, 14143, 14341, 14831, 15139, 15373, 16091, 17027, 17047, 19403, 20047, 20261, 21059, 21149, 22157, 23053, 23293, 23431, 24229, 24623
(list;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,1
|
|
COMMENTS
|
"SOD" = "sum of digits".
|
|
LINKS
|
|
|
FORMULA
|
Individually sum the digits of both prime index and associated prime. If both sums are prime and the sum of the index is the next prime of the prime SOD, add to sequence.
|
|
EXAMPLE
|
313 is a term, 65 is the index of the prime 313. The SOD(65) = 11. The SOD(313) = 7. 11 is the next prime after 7.
|
|
MATHEMATICA
|
Select[Range[25000], PrimeQ[#] && PrimeQ[Plus @@ IntegerDigits[#]] &&
NextPrime[Plus @@ IntegerDigits[#]] == Plus @@ IntegerDigits[PrimePi[#]] &] (* Tanya Khovanova, Mar 16 2021 *)
|
|
CROSSREFS
|
|
|
KEYWORD
|
easy,nonn,base
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|