David Applegate, _Marc LeBrun (mlb(AT)well.com) _ and N. J. A. Sloane, Aug 24 2010

_David Applegate (david(AT)research.att.com), _, Marc LeBrun (mlb(AT)well.com) and N. J. A. Sloane, Aug 24 2010

David Applegate (david(AT)research.att.com), Marc LeBrun (mlb(AT)well.com) and _N. J. A. Sloane (njas(AT)research.att.com), _, Aug 24 2010

<a href="/Sindx_index/Ca.html#CARRYLESS">Index entries for sequences related to carryless arithmetic</a>

<a href="/Sindx_Ca.html#CARRYLESS">Index entries for sequences related to carryless arithmetic</a>

nonn,base,new

A169887 = A163396 union A169985A169984.

nonn,base,new

a(n)=(product_{x=n-th even number..n-th even nonprime}x)/8

Primes in carryless arithmetic mod 10 in which all digits except the rightmost are even.

0, 3, 15, 42, 90, 165, 273, 420, 612, 855, 1155, 1518, 1950, 2457, 3045, 3720, 4488, 5355, 6327, 7410, 8610, 9933, 11385, 12972, 14700, 16575, 18603, 20790, 23142, 25665, 28365, 31248, 34320, 37587, 41055, 44730, 48618, 52725, 57057, 6162021, 23, 25, 27, 29, 41, 43, 45, 47, 49, 61, 63, 65, 67, 69, 81, 83, 85, 87, 89, 201, 209, 227, 229, 241, 243, 261, 263, 287, 289, 403, 407, 421, 427, 443, 449, 463, 469, 481, 487, 603, 607, 623, 629, 641, 647, 661, 667, 683, 689, 801, 809, 821

1,21

Here n-th even number = A005843(n), n-th even nonprime = A163300(n) (A014076 U A163300 = A141468).

These are called e-type primes.

<a href="Sindx_Ca.html#CARRYLESS">Index entries for sequences related to carryless arithmetic</a>

a(n)=(product_{x=n-th A005843..n-th A163300}x)/8.

a(1)=0/8=0, a(2)=2*3*4/8=3, a(3)=4*5*6/8=15.

Cf. A005843, A014076, A141468, A163300.

A169887 = A163396 union A169985.

nonn,base,new

Juri-Stepan Gerasimov David Applegate (david(AT)research.att.com), Marc LeBrun (mlb(AT)well.com) and N. J. A. Sloane (2stepannjas(AT)ramblerresearch.att.rucom), Jul 26 2009, Apr 22 Aug 24 2010

Corrected (110 replaced by 90, 25655 by 25665) by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 21 2010

a(n)=(product_{x=n-th even number..n-th even nonprime}x)/8

0, 3, 15, 42, 90, 165, 273, 420, 612, 855, 1155, 1518, 1950, 2457, 3045, 3720, 4488, 5355, 6327, 7410, 8610, 9933, 11385, 12972, 14700, 16575, 18603, 20790, 23142, 25665, 28365, 31248, 34320, 37587, 41055, 44730, 48618, 52725, 57057, 61620

1,2

Here n-th even number = A005843(n), n-th even nonprime = A163300(n) (A014076 U A163300 = A141468).

a(n)=(product_{x=n-th A005843..n-th A163300}x)/8.

a(1)=0/8=0, a(2)=2*3*4/8=3, a(3)=4*5*6/8=15.

Cf. A005843, A014076, A141468, A163300.

nonn,new

Juri-Stepan Gerasimov (2stepan(AT)rambler.ru), Jul 26 2009, Apr 22 2010

Corrected (110 replaced by 90, 25655 by 25665) by R. J. Mathar (mathar(AT)strw.leidenuniv.nl), May 21 2010

approved