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A340633 Primes of the form k + A037276(k). 3
2, 29, 41, 233, 239, 251, 257, 269, 293, 311, 359, 383, 401, 419, 449, 467, 491, 2269, 2309, 2339, 2377, 2381, 2393, 2411, 2417, 2447, 2473, 2503, 2543, 2579, 2591, 2621, 2633, 2671, 2687, 2699, 2713, 2753, 2789, 2797, 2819, 2843, 2879, 2939, 3011, 3041, 3067, 3083, 3119, 3137, 3167, 3191, 3203 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
All terms have first digit 2, 3 or 4.
LINKS
EXAMPLE
a(1) = 2 = 1 + A037276(1) = 1 + 1;
a(2) = 29 = 6 + A037276(6) = 6 + 23;
a(3) = 41 = 14 + A037276(14) = 14 + 27;
a(4) = 233 = 22 + A037276(22) = 22 + 211;
a(5) = 251 = 18 + A037276(18) = 18 + 233
= 34 + A037276(34) = 34 + 217.
MAPLE
N:= 5000: # for terms <= N
dcat:= proc(L) local i, x;
x:= L[-1];
for i from nops(L)-1 to 1 by -1 do
x:= 10^(1+ilog10(x))*L[i]+x
od;
x
end proc:
A037276:= proc(n) local F;
F:= sort(ifactors(n)[2], (a, b) -> a[1] < b[1]);
dcat(map(t -> t[1]$t[2], F));
end proc:
A037276(1):= 1:
R:= NULL:
for n from 1 to N/2 do
v:= n + A037276(n);
if v < N and isprime(v) then R:= R, v fi;
od:
sort(convert({R}, list));
CROSSREFS
Sequence in context: A260792 A059700 A078329 * A252892 A256472 A330895
KEYWORD
nonn,look,base
AUTHOR
J. M. Bergot and Robert Israel, Jan 13 2021
STATUS
approved

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Last modified June 20 03:21 EDT 2024. Contains 373512 sequences. (Running on oeis4.)