OFFSET
1,1
COMMENTS
a(26) > 10^10. a(27) = 1812918883. a(n) > 10^10 for n >= 28. - Donovan Johnson, May 08 2010
a(29) > 1.9*10^11. - Giovanni Resta, Aug 14 2013
FORMULA
MAPLE
A048853 := proc(n::integer) local resul, ddigs, d, c, tmp, tst ; resul := 0 ; ddigs := convert(n, base, 10) ; for d from 1 to nops(ddigs) do for c from 0 to 9 do if c = 0 and d = nops(ddigs) then continue ; else if c <> op(d, ddigs) then tmp := [op(1..d-1, ddigs), c, op(d+1..nops(ddigs), ddigs)] ; tst := sum(op(i, tmp)*10^(i-1), i=1..nops(tmp)) ; if isprime(tst) then resul := resul+1 ; fi ; fi ; fi ; od : od ; RETURN(resul) ; end: A050673 := proc(n::integer) local i, p; for p from 1 to 10000000 do i := ithprime(p) ; if A048853(i) = n then RETURN(i) ; fi ; od ; RETURN(-1) ; end : for n from 1 to 90 do print(A050673(n)) ; od ; # R. J. Mathar, Apr 25 2006
CROSSREFS
KEYWORD
nonn,base,more
AUTHOR
Patrick De Geest, Jul 15 1999
EXTENSIONS
a(22)-a(25) from Donovan Johnson, May 08 2010
a(26) and a(28) from Giovanni Resta, Aug 14 2013
STATUS
approved