|
| |
|
|
A156793
|
|
Indices of primes whose reversal is a different prime.
|
|
2
| |
|
|
6, 7, 11, 12, 20, 21, 22, 25, 28, 30, 35, 37, 39, 41, 46, 64, 68, 69, 72, 77, 126, 127, 130, 131, 132, 133, 135, 136, 155, 159, 160, 162, 163, 164, 166, 167, 169, 172, 173, 174, 178, 180, 182, 184, 185, 186, 190, 191, 194, 196, 197, 198, 199, 200, 201, 202, 203
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,1
|
|
|
COMMENTS
| Indices of primes in A006567.
|
|
|
LINKS
| Harvey P. Dale, Table of n, a(n) for n = 1..1000
|
|
|
EXAMPLE
| If prime(n=6)=13(1<3) and 31=prime, then 6=a(1). If prime(n=7)=17(1<7) and 71=prime, then 7=a(2). If prime(n=11)=31(3>1) and 13=prime, then 11=a(3), etc.
|
|
|
MATHEMATICA
| difpQ[n_]:=Module[{idn=IntegerDigits[n], ridn}, ridn=Reverse[idn]; idn!=ridn && PrimeQ[FromDigits[ridn]]]; PrimePi/@ Select[ Prime[ Range[ 250]], difpQ] (* From Harvey P. Dale, Nov 23 2011 *)
|
|
|
CROSSREFS
| Cf. A006567.
Sequence in context: A081359 A015825 A164018 * A081715 A054504 A190612
Adjacent sequences: A156790 A156791 A156792 * A156794 A156795 A156796
|
|
|
KEYWORD
| nonn,base
|
|
|
AUTHOR
| Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Feb 16 2009
|
|
|
EXTENSIONS
| 45 replaced by 46. 127, 131, 136, 155, 159 inserted, etc. - R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Feb 26 2009
|
| |
|
|
