A139182 Numbers m such that pi(m) = d_1!!*d_2!!*...*d_k!! where d_1 d_2 ... d_k is the decimal expansion of m.

50, 51, 125, 15405, 26205, 226700, 226701, 226710, 226711, 513090, 513091, 1351832, 8210065

Offset

1,1

Comments

Numbers m with a product of the double-factorials of the digits equal to A000720(m).

If { m is in the sequence, 10 divides m and m+1 is composite } then m+1 is in the sequence. [Clarified by N. J. A. Sloane, Feb 06 2022]

Links

Table of n, a(n) for n=1..13.

Example

pi(8210065)=8!!*2!!*1!!*0!!*0!!*6!!*5!!.

Mathematica

Select[Range[83*10^5], Times@@(IntegerDigits[#]!!)==PrimePi[#]&] (* Harvey P. Dale, Apr 12 2024 *)

Crossrefs

Cf. A066457, A006882.

Sequence in context: A043618 A296874 A134691 * A294297 A320673 A081646

Adjacent sequences: A139179 A139180 A139181 * A139183 A139184 A139185

Keyword

base,nonn,less,more

Author

Farideh Firoozbakht, Apr 19 2008

Status

approved