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A133958
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Home primes whose homeliness is 2.
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12
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37, 227, 229, 233, 241, 257, 271, 277, 283, 313, 317, 331, 347, 353, 359, 367, 383, 397, 523, 541, 557, 577, 719, 743, 761, 797, 1117, 1171, 1361, 1367, 1373, 1723, 1741, 1747, 1753, 1759, 1783, 1789, 1973, 1979, 1997, 2113, 2131, 2137, 2179, 2213, 2239
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Number of terms < 10^n: 0, 1, 26, 182, 1428, 10395, 84164, ....
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EXAMPLE
| Only {21 & 37} -> 37, etc.
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MATHEMATICA
| 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}];
d = 2 - 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, 50]
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CROSSREFS
| Cf. A037274, A118756, A133957, A133956, A000014, A133960, A133962, A133964, A133966, A133968, A133970, A133972, A133974, A133976, A133978.
Sequence in context: A141984 A052166 A142010 * A088544 A051463 A142445
Adjacent sequences: A133955 A133956 A133957 * A133959 A133960 A133961
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KEYWORD
| nonn
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AUTHOR
| Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 30 2007
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