A048549
a(n+1) is next smallest prime beginning with a(n), initial prime is 2.
Original entry on oeis.org
2, 23, 233, 2333, 23333, 2333321, 233332117, 2333321173, 233332117313, 23333211731399, 2333321173139903, 2333321173139903173, 23333211731399031733, 2333321173139903173301, 2333321173139903173301021
Offset: 1
Similar to but different from
A069603.
-
b = 10; s = {{2}};
Do[NestWhile[# + 1 &, 0, ! (PrimeQ[FromDigits[tmp = Join[Last[s], (nn = #;
IntegerDigits[nn - Sum[b^n, {n, l = NestWhile[# + 1 &, 1, ! (nn - (Sum[b^n, {n, #}]) < 0) &] - 1}], b, l + 1])], b]]) &]; AppendTo[s, tmp], {20}]; Map[FromDigits, s] (* Peter J. C. Moses, Aug 06 2015 *)
A048552
a(n+1) is next smallest prime beginning with a(n), initial prime is a(0) = 7.
Original entry on oeis.org
7, 71, 719, 7193, 71933, 719333, 71933317, 719333177, 71933317711, 7193331771103, 71933317711039, 7193331771103939, 719333177110393913, 7193331771103939133, 719333177110393913323, 71933317711039391332309, 719333177110393913323097, 719333177110393913323097047
Offset: 0
-
f:= proc(n) option remember; local q,d,v;
q:=procname(n-1);
for d from 1 do
v:= nextprime(q*10^d);
if v < (q+1)*10^d then return v fi
od
end proc:
f(0):= 7:
map(f, [$0..20]); # Robert Israel, Jan 26 2020
-
Nest[Function[{a, n}, Append[#, Catch@ Do[Do[If[PrimeQ@ #, Throw@ #; Break[], #] &@ FromDigits[n~Join~PadLeft[IntegerDigits[(5 j - 4 + Mod[3 j + 2, 4])/2], i]], {j, 4*10^(i - 1)}], {i, Infinity}]]] @@ {#, IntegerDigits[#[[-1]] ]} &, {7}, 17] (* Michael De Vlieger, Jan 26 2020 *)
-
next_A048552(p)=for(i=1,oo,my(q=nextprime(p*=10));q-p>10^i||return(q))
A048552(n,p=7)=vector(n,i,i>1&&p=next_A048552(p);p) \\ M. F. Hasler, Jan 26 2020
A100894
a(n) = smallest n-digit prime formed by appending a digit to a(n-1); a(1) = 3.
Original entry on oeis.org
3, 31, 311, 3119, 31193
Offset: 1
a(1)=3
a(2)=31
a(3)=311
a(4)=3119
a(5)=31193
Showing 1-3 of 3 results.
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