A092620 - OEIS

A092620

Numbers with exactly one prime digit.

2, 3, 5, 7, 12, 13, 15, 17, 20, 21, 24, 26, 28, 29, 30, 31, 34, 36, 38, 39, 42, 43, 45, 47, 50, 51, 54, 56, 58, 59, 62, 63, 65, 67, 70, 71, 74, 76, 78, 79, 82, 83, 85, 87, 92, 93, 95, 97, 102, 103, 105, 107, 112, 113, 115, 117, 120, 121, 124, 126, 128, 129, 130, 131, 134

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,1

COMMENTS

A193238(a(n))=1; subsequence of A118950. - Reinhard Zumkeller, Jul 19 2011

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..10000

FORMULA

There are 6^n*(n-1/6)*2/3 n-digit members of this sequence for n > 1. - Charles R Greathouse IV, Apr 23 2022

EXAMPLE

12 has one prime digit, 2;

102 has one prime digit, 2.

MAPLE

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_n:=proc(n) local i, stpf, ans, ans1, tren; ans:=[ ]: stpf:=0: tren:=1: for i from 1 to n do if ( isprime(i)='true' and ts_stpf(i) =0) then ans:=[ op(ans), i ]: tren:=tren+1; fi od; RETURN(ans) end: ts_pr_n(300);

MATHEMATICA

Select[Range[150], Count[IntegerDigits[#], _?(PrimeQ)]==1&] (* Harvey P. Dale, Mar 23 2018 *)

PROG

(Haskell)

import Data.List (elemIndices)

a092620 n = a092620_list !! (n-1)

a092620_list = elemIndices 1 a193238_list

-- Reinhard Zumkeller, Jul 19 2011

CROSSREFS

Subsequence of A118950.

Cf. A046034, A084984, A092624, A092625.

Sequence in context: A114983 A118950 A344451 * A028843 A028842 A260181

Adjacent sequences: A092617 A092618 A092619 * A092621 A092622 A092623

KEYWORD

nonn,base,easy

AUTHOR

Jani Melik, Apr 11 2004

STATUS

approved