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A067227 n is prime and remains prime when its leading digit is replaced by each of 2, 4 and 8. 1
13, 23, 43, 53, 73, 83, 139, 157, 163, 239, 257, 263, 439, 457, 463, 557, 563, 739, 757, 839, 857, 863, 1297, 1423, 1447, 1663, 1861, 1999, 2111, 2243, 2273, 2297, 2423, 2447, 2663, 2861, 2969, 2999, 4111, 4243, 4273, 4297, 4423, 4447, 4663, 4861, 4969 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

2, 4 and 8 were chosen because they are powers of 2.

LINKS

Harvey P. Dale, Table of n, a(n) for n = 1..1000

EXAMPLE

53 is prime and so are 23, 43, 83, so 53 is a term of the sequence.

MATHEMATICA

(*replaces the leading digit of n by m*) f[n_, m_] := FromDigits[Flatten[Append[IntegerDigits[m], Drop[IntegerDigits[n], 1]]]]; Select[Range[10^4], PrimeQ[ # ] && PrimeQ[f[ #, 2]] && PrimeQ[f[ #, 4]] && PrimeQ[f[ #, 8]] & ]

Select[Prime[Range[700]], AllTrue[FromDigits/@Table[Join[{i}, Rest[ IntegerDigits[ #]]], {i, {2, 4, 8}}], PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Jun 04 2017 *)

CROSSREFS

Sequence in context: A165350 A236418 A112394 * A240113 A256177 A320752

Adjacent sequences:  A067224 A067225 A067226 * A067228 A067229 A067230

KEYWORD

base,nonn

AUTHOR

Joseph L. Pe, Feb 20 2002

EXTENSIONS

Offset corrected to 1 and title simplified by M. F. Hasler, Nov 01 2014

STATUS

approved

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Last modified September 26 06:16 EDT 2021. Contains 347664 sequences. (Running on oeis4.)