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A235687 Semiprimes which remain semiprimes when the rightmost digit is removed. 3
46, 49, 62, 65, 69, 91, 93, 94, 95, 106, 141, 142, 143, 145, 146, 155, 158, 159, 213, 214, 215, 217, 218, 219, 221, 226, 253, 254, 259, 262, 265, 267, 334, 335, 339, 341, 346, 355, 358, 381, 382, 386, 391, 393, 394, 395, 398, 466, 469, 493, 497, 511, 514 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

EXAMPLE

514 is in the sequence because 51 = 3*17.

MATHEMATICA

Select[Range[600], PrimeOmega[#]==2==PrimeOmega[FromDigits[ Most[ IntegerDigits[ #]]]]&] (* Harvey P. Dale, Oct 02 2014 *)

PROG

(PARI)

list(lim)=my(v=List(), t); forprime(p=2, sqrt(lim), t=p; forprime(q=p, lim\t, listput(v, t*q))); vecsort(Vec(v)) \\ From A001358

issemiprime(n) = n>0 && bigomega(n)==2

t=list(1000); for(n=1, #t, if(issemiprime(t[n]\10), print1(t[n], ", ")))

CROSSREFS

Cf. A235688, A235689.

Cf. A227919, A227916, A069686.

Sequence in context: A282465 A098194 A181460 * A321046 A269671 A039354

Adjacent sequences:  A235684 A235685 A235686 * A235688 A235689 A235690

KEYWORD

nonn,base

AUTHOR

Colin Barker, Jan 14 2014

STATUS

approved

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Last modified September 18 01:03 EDT 2021. Contains 347498 sequences. (Running on oeis4.)