Re: Integer Assumptions in Integrations

*To*: mathgroup at smc.vnet.net*Subject*: [mg20179] Re: [mg20153] Integer Assumptions in Integrations*From*: BobHanlon at aol.com*Date*: Sun, 3 Oct 1999 21:07:43 -0400*Sender*: owner-wri-mathgroup at wolfram.com

Will, Integrate[t^(a - 1)*Exp[-t], {t, q, Infinity}] Gamma[a, q] This answer is not simpler for integers. I think you want FunctionExpand Table[Gamma[a, q], {a, 5}] // FunctionExpand // Simplify {E^(-q), (q + 1)/E^q, (q^2 + 2*q + 2)/E^q, (q^3 + 3*q^2 + 6*q + 6)/E^q, (q^4 + 4*q^3 + 12*q^2 + 24*q + 24)/E^q} Bob Hanlon In a message dated 10/2/1999 8:11:29 AM, wcooper1 at san.rr.com writes: >How can I set a variable assumption to be an integer in an integration > >calculation? > >e.g. The incomplete gamma function is defined as Gamma[a,q] = >Integrate[t^(a-1)*Exp[-t], {t, q, Infinity}] > >I want to set the assumption that 'a' is always an Integer. > >I don't want to round 'a' to the next lowest integer, i.e. >Integrate[t^(Integer[a]-1)*Exp[-t], {t, q, Infinity}] > >I just want to indicate that 'a' only assumes integer values. >