_Reinhard Zumkeller_, , <a href="/A092624/b092624.txt">Table of n, a(n) for n = 1..10000</a>

_Reinhard Zumkeller, _, <a href="/A092624/b092624.txt">Table of n, a(n) for n = 1..10000</a>

-- _Reinhard Zumkeller, _, Jul 19 2011

A193238(a(n))=2; subsequence of A118950. [_Reinhard Zumkeller, _, Jul 19 2011]

_Jani Melik (jani_melik(AT)hotmail.com), _, Apr 11 2004

proposed

approved

editing

proposed

A193238(a(n))=2; subsequence of A118950. [Reinhard Zumkeller, Jul 19 2011]

Reinhard Zumkeller, <a href="/A092624/b092624.txt">Table of n, a(n) for n = 1..10000</a>

(Haskell)

import Data.List (elemIndices)

a092624 n = a092624_list !! (n-1)

a092624_list = elemIndices 2 a193238_list

-- Reinhard Zumkeller, Jul 19 2011

Cf. A084984, A092620, A092625.

approved

editing

proposed

approved

Numbers with exactly two prime digits.

nonn,base,new

approved

proposed

Numbers with two prime digits.

22, 23, 25, 27, 32, 33, 35, 37, 52, 53, 55, 57, 72, 73, 75, 77, 122, 123, 125, 127, 132, 133, 135, 137, 152, 153, 155, 157, 172, 173, 175, 177, 202, 203, 205, 207, 212, 213, 215, 217, 220, 221, 224, 226, 228, 229, 230, 231, 234, 236, 238, 239, 242, 243, 245

1,1

25 has two prime digits, 2 and 5;

207 has two prime digits, 2 and 7.

stev_sez:=proc(n) local i, tren, st, ans, anstren; ans:=[ ]: anstren:=[ ]: tren:=n: for i while (tren>0) do st:=round( 10*frac(tren/10) ): ans:=[ op(ans), st ]: tren:=trunc(tren/10): end do; for i from nops(ans) to 1 by -1 do anstren:=[ op(anstren), op(i, ans) ]; od; RETURN(anstren); end: ts_stpf:=proc(n) local i, stpf, ans; ans:=stev_sez(n): stpf:=0: for i from 1 to nops(ans) do if (isprime(op(i, ans))='true') then stpf:=stpf+1; # number of prime digits fi od; RETURN(stpf) end: ts_pr_nd:=proc(n) local i, stpf, ans, ans1, tren; ans:=[ ]: stpf:=0: tren:=1: for i from 1 to n do if ( ts_stpf(i) = 2) then ans:=[ op(ans), i ]: tren:=tren+1; fi od; RETURN(ans) end: ts_pr_nd(500);

Cf. A034895, A046034, A085557, A019546, A034844.

nonn

Jani Melik (jani_melik(AT)hotmail.com), Apr 11 2004

approved