A199987 -id:A199987 - cp's OEIS frontend

A107690 Primes with digital product = 4.

41, 4111, 11411, 12211, 21121, 21211, 22111, 112121, 1114111, 11111141, 11141111, 111112121, 111121121, 112111211, 112112111, 121111121, 121112111, 122111111, 212111111, 1111111411, 1111411111, 11111121121, 11111121211, 11111211121

Offset: 1

Zak Seidov and Robert G. Wilson v, May 20 2005

Vincenzo Librandi, Table of n, a(n) for n = 1..2400

Cf. A004022, A107612, A107689, A107691, A107692, A107693, A107694, A107695, A107696, A107697, A107698.

Subsequence of A199987.

[p: p in PrimesUpTo(10^8) | &*Intseq(p) eq 4]; // Vincenzo Librandi, Jun 30 2017

Flatten[ Table[ Select[ Sort[ FromDigits /@ Join[ Permutations[ Flatten[{4, Table[1, {n}]}]], Permutations[ Flatten[{2, 2, Table[1, {n - 1}]}] ]]], PrimeQ[ # ] &], {n, 0, 10}]]

A201016 Composite numbers whose product of digits is 4.

Original entry on oeis.org

4, 14, 22, 114, 122, 141, 212, 221, 411, 1114, 1122, 1141, 1212, 1221, 1411, 2112, 2121, 2211, 11114, 11122, 11141, 11212, 11221, 12112, 12121, 14111, 21112, 41111, 111114, 111122, 111141, 111212, 111221, 111411, 112112, 112211, 114111, 121112, 121121, 121211, 122111

Offset: 1

Jaroslav Krizek, Nov 25 2011

Complement of A107690 with respect to A199987. Subsequence of A199983 (composite numbers whose multiplicative digital root is 4).

			Number 122 is in sequence because 1*2*2=4.

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Cf. A107690 (primes whose product of digits is 4), A199987 (numbers whose product of digits is 4).

Select[Range[125000],CompositeQ[#]&&Times@@IntegerDigits[#]==4&] (* or *) Module[{nn=6,f,t},f=Flatten[Table[Select[FromDigits/@Permutations[PadRight[{4},d,1]],CompositeQ],{d,nn}]];t=Flatten[Table[Select[FromDigits/@Permutations[PadRight[{2,2},d,1]],CompositeQ],{d,nn}]];Join[f,t]]//Sort (* The second program is much faster than the first. *) (* Harvey P. Dale, May 15 2025 *)

cp's OEIS Frontend

A107690 Primes with digital product = 4.

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