OFFSET
1,1
EXAMPLE
Both 97 = prime(25) and 25 have digital root = 7,
both 131 = prime(32) and 32 have digital root = 5.
MATHEMATICA
Reap[Do[If[FixedPoint[Total[IntegerDigits[#]]&, n]==Mod[(p=Prime[n]), 9], Sow[p]], {n, 439}]][[2, 1]]
Prime[Select[Range@370, Mod[#, 9]==Mod[Prime[#], 9]&]] (* Ivan N. Ianakiev, Jun 18 2015 *)
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Zak Seidov, Jun 13 2015
STATUS
approved