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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. 1
50, 51, 125, 15405, 26205, 226700, 226701, 226710, 226711, 513090, 513091, 1351832, 8210065 (list; graph; refs; listen; history; text; internal format)
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
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
Sequence in context: A043618 A296874 A134691 * A294297 A320673 A081646
KEYWORD
base,nonn,less,more
AUTHOR
Farideh Firoozbakht, Apr 19 2008
STATUS
approved

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Last modified May 25 09:23 EDT 2024. Contains 372786 sequences. (Running on oeis4.)