A197817 Smallest composite m such that m and the smallest prime divisor of m begin with n.
121, 20, 33, 4141, 55, 6161, 77, 8051, 9409, 10201, 1111, 120269, 1313, 140209, 150547, 160229, 1717, 180457, 1919, 20002379, 210367, 220417, 2323, 240277, 250247, 260123, 270187, 280157, 2929, 301781, 3131, 32003357, 330007, 340973, 350743, 360761, 3737, 380053
Offset: 1
Examples
a(8) = 8051 = 83*97 => 8051 and 83 start with 8.
Programs
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Maple
with(numtheory): for n from 1 to 60 do: l1:=length(n):i:=0:for m from 2 to 32*10^6 while(i=0) do: x:=factorset(m):y:=x[1]: l2:=length(m):x1:=floor(m/(10^(l2-l1))): l3:=length(y):x2:=floor(y/(10^(l3-l1))):if x1=n and x2=n and l2>=l1 and l3 >=l1 and type(m,prime)=false then i:=1: printf ( "%d %d \n",n,m):else fi :od:od:
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