A215419:=proc(q, x)
local a, b, c, d, i, n, ok;
for n from 1 to q do
a:=ithprime(n); b:=0; while a>0 do b:=b+1; a:=trunc(a/10); od;
a:=ithprime(n); ok:=1;
for i from 0 to b do
c:=a+9*10^i*trunc(a/10^i)+10^i*x; if not isprime(c) then ok:=0; break; fi;
od;
if ok=1 then print(ithprime(n)); fi;
od; end:
A215419(1000, 3);
# Alternative:
approved
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editing
proposed
# Alternative code
P:=proc(q) local a, k, n, v; v:=[]; for n from 0 to q do a:=convert(n, base, 10);
if n=add(a[-k]^k, k=1..nops(a)) then v:=[op(v), n]; fi; od; op(v); end: P(3*10^6); # Paolo P. Lava, Oct 29 2024
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# Alternative code
P:=proc(q) local a, k, n, v; v:=[]; for n from 0 to q do a:=convert(n, base, 10);
if n=add(a[-k]^k, k=1..nops(a)) then v:=[op(v), n]; fi; od; op(v); end: P(3*10^6); Paolo P. Lava, Oct 29 2024
proposed
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allocated for Paolo P. Lava
Least integer k such that, through a process analogous to the Keith numbers, it reaches k - n.
14, 18, 10, 11, 12, 10, 11, 10, 10, 10, 20, 27, 22, 25, 20, 23, 20, 21, 20, 38, 32, 30, 31, 34, 30, 32, 31, 30, 40, 47, 41, 45, 40, 43, 42, 41, 40, 58, 51, 56, 50, 54, 53, 52, 51, 50, 61, 67, 60, 65, 64, 63, 62, 61, 60, 78, 70, 76, 75, 74, 73, 72, 71, 70, 80, 87
0,1
a(6) = 11 because 1 + 1 = 2, 1 + 2 = 3, 2 + 3 = 5 that is 11 - 6.
with(numtheory): P:=proc(q, h) local a, b, c, j, k, n, t, v; v:=array(1..h); c:=[];
for j from 0 to 65 do for n from 10 to q do a:=n; b:=length(a);
for k from 1 to b do v[b-k+1]:=(a mod 10); a:=trunc(a/10); od; t:=b+1; v[t]:=add(v[k], k=1..b);
while v[t]<n-j do t:=t+1; v[t]:=add(v[k], k=t-b..t-1); od; if v[t]=n-j then c:=[op(c), n];
break; fi; od; od; op(c); end: P(10^6, 5000);
allocated
nonn,easy,base
Paolo P. Lava, Oct 28 2024
approved
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allocated for Paolo P. Lava
allocated
approved