A133962 - OEIS

%I #11 Mar 23 2021 15:42:36

%S 379,2347,2383,2389,3331,3359,3373,3719,3767,4397,4759,7331,7457,7523,

%T 7547,7823,11251,13883,17137,17317,19157,19181,22367,22397,23131,

%U 23173,23197,23311,23593,23677,23767,23911,29101,31063,31123,31181,31189

%N Home primes whose homeliness is 4.

%C Number of terms < 10^n: 0, 0, 1, 16, 146, 1085, 8522, ... .

%e Only (42,74,237,379) -> 379, etc.

%t lst = {}; f[n_] := FromDigits@ Flatten[ IntegerDigits@ Table[ #[[1]], {#[[2]]}] & /@ FactorInteger@n, 2]; h[n_] := NestWhileList[f@# &, n, !PrimeQ@# &, 1, 28]; Do[p = h[n][[ -1]]; If[ PrimeQ@p && p < 10^7 && p != n, Print[{n, p}]; AppendTo[lst, p]], {n, 2, 1000}];

%t d = 4 - 2; lsu = {}; Do[ If[ lst[[n]] == lst[[n + d]] && lst[[n - 1]] != lst[[n]] && lst[[n]] != lst[[n + d + 1]], AppendTo[lsu, lst[[n]]]], {n, 188004 - d - 1}]; Take[Union@ lsu, 45]

%Y Cf. A037274, A118756, A133961, A133956, A133957, A133958, A133960, A133964, A133966, A133968, A133970, A133972, A133974, A133976, A133978.

%K nonn,base

%O 1,1

%A _Robert G. Wilson v_, Sep 30 2007