A378627 Products of 6 distinct primes that are sandwiched between semiprime (or biprime) numbers.

39270, 66990, 71610, 79170, 82110, 99330, 110670, 122430, 123690, 125970, 129030, 132090, 136290, 144690, 152490, 163590, 166530, 167790, 180642, 182910, 190190, 191730, 215670, 220110, 222222, 226590, 227766, 231990, 235410, 239190, 247170, 248710, 249690, 254562, 258258, 260130

Offset

1,1

Comments

All terms are even.

All terms are divisible by 6. Since they are products of distinct primes, i.e. 3 is at an odd power, they are all Zumkeller numbers (A083207). - Ivan N. Ianakiev, Dec 16 2024

Links

Table of n, a(n) for n=1..36.

Example

39270 is a term because 39270=2*3*5*7*11*17 is the product of six distinct primes, 39269=107*367 and 39271=173*227 are both semiprimes.
66990 is a term because 66990=2*3*5*7*11*29 is the product of six distinct primes, 66989=13*5153 and 66991=31*2161 are both semiprimes.

Mathematica

SequencePosition[Array[FactorInteger[#][[;; , 2]] &, 270000] /. {2} -> {1, 1}, {{1, 1}, {1, 1, 1, 1, 1, 1}, {1, 1}}][[;; , 1]] + 1 (* Amiram Eldar, Dec 02 2024 *)

Crossrefs

Cf. A067885, A001358, A378097, A083207 (supersequence).

Sequence in context: A250515 A031667 A196200 * A274128 A144306 A234033

Adjacent sequences: A378624 A378625 A378626 * A378628 A378629 A378630

Keyword

nonn,new

Author

Massimo Kofler, Dec 02 2024

Status

approved