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A161720 a(n) = (prime(n) - 7)/2. 0
-1, 0, 2, 3, 5, 6, 8, 11, 12, 15, 17, 18, 20, 23, 26, 27, 30, 32, 33, 36, 38, 41, 45, 47, 48, 50, 51, 53, 60, 62, 65, 66, 71, 72, 75, 78, 80, 83, 86, 87, 92, 93, 95, 96, 102, 108, 110, 111, 113, 116, 117, 122, 125, 128, 131, 132 (list; graph; refs; listen; history; text; internal format)
OFFSET

3,3

COMMENTS

Original name was: Half the difference between the first and the last numbers in the 7th circle of the cyclic representation of some structures whose cardinality generates Aminu numbers.

A bijective operator is defined on the Aminu numbers which in turn generates another cyclic group. Aminu numbers were first reported as the cardinality of some subgroups of regular groups whose order and degree coincide (Ibrahim,2004;2005;2007 and Ibrahim and Audu 2005). The action of the operator on the group structures where constructed using some special succession scheme which led to sequences such as A005097. This sequence enumerates half the difference between the first and last numbers in the 7th cycle of such group structures.

REFERENCES

A. A. Ibrahim, Group theoretic interpretation of Bara'a al-Dhimmah Models: Proceedings of Annual National Conference of Mathematical Association of Nigeria, MAN,(2004), 35-40.

A. A. Ibrahim and M. S. Audu, Some Group Theoretic Properties of Certain class of (123) and (132)- Avoiding Patterns of numbers: An enumeration scheme,African Journal of Natural Sciences, 8(1)(2005), 79-84.

A. A. Ibrahim, An Enumeration scheme and Algebraic properties of a special (132)- avoiding class of permutations Patterns, Trends in Applied sciences Research, Academic Journal Inc. 2(4)(2007), 334-340.

LINKS

Table of n, a(n) for n=3..58.

FORMULA

a(n) = A105760(n-3). - R. J. Mathar, Sep 11 2012

EXAMPLE

For Pn=5, a(1)=-2/2=-1, for Pn=7, a(2)=0/2=0, for Pn=11,a(3)=4/2=2

PROG

(PARI) a(n)=(prime(n)-7)/2 \\ Charles R Greathouse IV, Jun 15 2013

CROSSREFS

Cf. A178674, A000040, A005097.

Essentially a duplicate of A105760.

Sequence in context: A266409 A035057 A005099 * A105760 A050834 A294911

Adjacent sequences:  A161717 A161718 A161719 * A161721 A161722 A161723

KEYWORD

sign,easy,less

AUTHOR

G. A. Isa (isaabor(AT)yahoo.com), Jun 18 2009

EXTENSIONS

Name changed by Arkadiusz Wesolowski, Jun 15 2013

STATUS

approved

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Last modified August 9 02:14 EDT 2020. Contains 336310 sequences. (Running on oeis4.)