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A349455
Members of A014574 with sum of prime factors (with multiplicity) also in A014574.
1
4, 42, 60, 72, 618, 1488, 2730, 4230, 6762, 8010, 8232, 8538, 9282, 12540, 12822, 13008, 15582, 19212, 20898, 24420, 24918, 26712, 32718, 41412, 41610, 43542, 45318, 46830, 49530, 50130, 51060, 53172, 53550, 55662, 56598, 58230, 58368, 61560, 62130, 69930, 71712, 72090, 72222, 75402, 77688, 78192
OFFSET
1,1
COMMENTS
Numbers k such that k-1, k+1, A001414(k)-1 and A001414(k)+1 are all prime.
LINKS
EXAMPLE
a(3) = 60 is a term because 60-1 = 59 and 60+1 = 61 are primes, A001414(60) = 2+2+3+5 = 12, and 12-1 = 11 and 12+1 = 13 are primes.
MAPLE
spf:= proc(n) local F, t;
F:= ifactors(n)[2];
add(t[1]*t[2], t=F)
end proc:
R:= 4: count:= 1:
for t from 6 by 6 while count < 100 do
if isprime(t-1) and isprime(t+1) then
s:= spf(t);
if isprime(s-1) and isprime(s+1) then
count:= count+1;
R:= R, t;
fi
fi
od:
R;
MATHEMATICA
Select[Prime@Range@8000, PrimeQ[#+2]&&And@@PrimeQ[Total[Flatten[Table@@@FactorInteger[#+1]]]+{1, -1}]&]+1 (* Giorgos Kalogeropoulos, Nov 18 2021 *)
CROSSREFS
Sequence in context: A320335 A076652 A078288 * A089551 A347320 A220835
KEYWORD
nonn
AUTHOR
J. M. Bergot and Robert Israel, Nov 17 2021
STATUS
approved