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A155034
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Primes with smallest digit odd and prime (i.e., 3, 5 or 7).
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1
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3, 5, 7, 37, 43, 53, 59, 73, 79, 83, 97, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 433, 439, 443, 463, 557, 563, 569, 577, 587, 593, 599, 643, 653, 659, 673, 683, 733, 739, 743, 757, 773, 787, 797, 839, 853, 857, 859, 863, 877, 883, 887, 937, 953, 977
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OFFSET
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1,1
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COMMENTS
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LINKS
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MAPLE
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N:= 4: # to get all terms with <+ N digits
for j in [3, 5, 7] do L[1, j]:= {$j..9}; C[1, j]:= {j} od;
for d from 2 to N do
for j in [3, 5, 7] do L[d, j]:= map(t -> $(10*t+j)..(10*t+9), L[d-1, j]) od:
C[d, 3]:= map(t -> (10*t+3), L[d-1, 3]) union map(t ->seq(10*t+j, j=4..9), C[d-1, 3]);
C[d, 5]:= map(t -> (10*t+5), L[d-1, 5]) union map(t -> seq(10*t+j, j=6..9), C[d-1, 5]);
C[d, 7]:= map(t -> (10*t+7), L[d-1, 7]) union map(t -> seq(10*t+j, j=8..9), C[d-1, 7]);
od:
sort(convert(`union`(seq(seq(select(isprime, C[d, j]), j=[3, 5, 7]), d=1..N)), list));
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PROG
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(PARI) is(n) = ispseudoprime(n) && #setintersect(Set(vecmin(digits(n))), [3, 5, 7])==1 \\ Felix Fröhlich, Jan 26 2017
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CROSSREFS
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KEYWORD
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nonn,base,less
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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