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A097221 Numbers n such that for some k and a_1,a_2,...,a_k the concatenation of the a_i is equal to n and their product is equal to pi(n). 3
16, 17, 63, 73, 132, 224, 322, 342, 352, 362, 364, 437, 545, 573, 619, 963, 1017, 1117, 1196, 1516, 2163, 2215, 2335, 2435, 2537, 3277, 3514, 3714, 4072, 4513, 4626, 5137, 6475, 8443, 11373, 11593, 11926, 12012, 12026, 12034, 12121, 12126, 12134, 12555 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
A097220 is a subsequence of this sequence.
LINKS
EXAMPLE
90942236 is in the sequence because Pi(90942236)=909*42*23*6 in fact a1=909, a2=42, a3=23 & a4=6.
PROG
(PARI) composed(n, a)=my(d=0, k); if(a>=n, return(a==n)); while(10^d<n, k=n%10^d++; if(k>0&a%k==0&composed(n\10^d, a/k), return(1))); 0
isA097221(n)=composed(n, primepi(n))
CROSSREFS
Sequence in context: A041524 A042205 A041522 * A097220 A041530 A041528
KEYWORD
nonn,base
AUTHOR
Farideh Firoozbakht, Aug 05 2004
EXTENSIONS
Corrected (2537,3277,4513,4626 were missing), extended, edited, and program added by Charles R Greathouse IV, Apr 23 2010
STATUS
approved

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Last modified July 15 10:49 EDT 2024. Contains 374332 sequences. (Running on oeis4.)